Method for transmitting and receiving synchronization signal block and apparatus therefor

ABSTRACT

Disclosed is a method for a terminal to receive a synchronization signal block (SSB) in a wireless communication system. In particular, the method comprises receiving, on a first half frame or a second half frame included in a wireless frame, at least one SSB mapped to a plurality of symbols, wherein the at least one SSB is any one of a first SSB received on the first half frame and a second SSB received on the second half frame, and a signal of the same type is mapped to a first symbol included in a plurality of symbols to which the first SSB is mapped and a second symbol included in a plurality of symbols to which the second SSB is mapped, but a phase of the first symbol and a phase of the second symbol are different.

TECHNICAL FIELD

The present disclosure relates to a method of transmitting and receivinga synchronization signal block and an apparatus therefor and, moreparticularly, to a method of identifying a half-frame in which asynchronization signal block is transmitted through phases of symbols towhich the synchronization signal block is mapped, and an apparatustherefor.

BACKGROUND ART

As more and more communication devices demand larger communicationtraffic along with the current trends, a future-generation 5thgeneration (5G) system is required to provide an enhanced wirelessbroadband communication, compared to the legacy LTE system. In thefuture-generation 5G system, communication scenarios are divided intoenhanced mobile broadband (eMBB), ultra-reliability and low-latencycommunication (URLLC), massive machine-type communication (mMTC), and soon.

Herein, eMBB is a future-generation mobile communication scenariocharacterized by high spectral efficiency, high user experienced datarate, and high peak data rate, URLLC is a future-generation mobilecommunication scenario characterized by ultra high reliability, ultralow latency, and ultra high availability (e.g., vehicle to everything(V2X), emergency service, and remote control), and mMTC is afuture-generation mobile communication scenario characterized by lowcost, low energy, short packet, and massive connectivity (e.g., Internetof things (IoT)).

DETAILED DESCRIPTION OF THE DISCLOSURE Technical Problems

The present disclosure is to provide a method of transmitting andreceiving a synchronization signal block and an apparatus therefor.

The objects to be achieved with the present disclosure are not limitedto what has been particularly described hereinabove and other objectsnot described herein will be more clearly understood by persons skilledin the art from the following detailed description.

Technical Solutions

According to an aspect of the present disclosure, provided herein is amethod of receiving a synchronization signal block (SSB) by a userequipment (UE) in a wireless communication system, including receivingat least one SSB mapped to a plurality of symbols in a first half-frameor a second half-frame included in a radio frame. The at least one SSBmay be any one of a first SSB received in the first half-frame and asecond SSB received in the second half-frame. A signal of the same typemay be mapped to a first symbol included in a plurality of symbols towhich the first SSB is mapped and a second symbol included in aplurality of symbols to which the second SSB is mapped. Phases of thefirst symbol and the second symbol may be different.

The signal of the same type may be any one of a primary synchronizationsignal (PSS), a secondary synchronization signal (SSS), and a physicalbroadcasting channel (PBCH).

The phases of the first symbol and the second symbol may have adifference of 180 degrees.

The at least one SSB may include a physical broadcasting channel (PBCH)including an indicator for distinguishing between the first half-frameand the second half-frame, and the indicator may be used to generate ascrambling sequence of the PBCH.

A demodulation reference signal (DMRS) may be mapped to a symbol towhich the PBCH is mapped, and a sequence of the DMRS may be generatedbased on the number of SSB indexes obtainable through the DMRS and onthe indicator.

The sequence of the DMRS may be generated based on multiplication of thenumber of the SSB indexes obtainable through the DMRS and a valueindicated by the indicator.

Based on detection of the first SSB, the UE may perform detection of thesecond SSB in a specific time duration after a predetermined time from atiming at which the first SSB is detected.

A demodulation reference signal (DMRS) may be mapped to a symbol towhich a physical broadcasting channel (PBCH) included in each of thefirst SSB and the second SSB is mapped, and a sequence of a DMRS relatedwith the first SSB may be different from a sequence of a DMRS relatedwith the second SSB.

A demodulation reference signal (DMRS) may be mapped to a symbol towhich a physical broadcasting channel (PBCH) included in each of thefirst SSB and the second SSB is mapped, and a frequency position towhich a DMRS related with the first SSB is mapped may be different froma frequency position to which a DMRS related with the second SSB ismapped.

Based on initial access performed by the UE, the at least one SSB may berepeatedly transmitted at a first time periodicity, and based on radioresource control (RRC) connection state of the UE, the at least one SSBmay be repeatedly transmitted at a second time periodicity longer thanthe first time periodicity.

Based on assumption that signals transmitted from a serving cell and aneighbor cell of the UE are received within a predetermined error range,time information obtained through an SSB received from the serving cellmay be equally applied to an SSB received from the neighbor cell.

In another aspect of the present disclosure, provided herein is a userequipment (UE) for receiving a synchronization signal block (SSB) in awireless communication system, including a transceiver configured totransmit and receive a signal to and from a base station (BS), and aprocessor connected to the transceiver and configured to control thetransceiver to receive at least one SSB mapped to a plurality of symbolsin a first half-frame or a second half-frame included in a radio frame.The at least one SSB may be any one of a first SSB received in the firsthalf-frame and a second SSB received in the second half-frame. A signalof the same type may be mapped to a first symbol included in a pluralityof symbols to which the first SSB is mapped and a second symbol includedin a plurality of symbols to which the second SSB is mapped. Phases ofthe first symbol and the second symbol may be different.

In another aspect of the present disclosure, provided herein is a methodof transmitting a synchronization signal block (SSB) by a base station(BS) in a wireless communication system, including mapping at least oneSSB to a plurality of symbols and transmitting the at least one SSB in afirst half-frame or a second half-frame included in a radio frame. Afirst SSB may be transmitted in the first half-frame and a second SSBmay be transmitted in the second half-frame. A signal of the same typemay be mapped to a first symbol included in a plurality of symbols towhich the first SSB is mapped and a second symbol included in aplurality of symbols to which the second SSB is mapped. Phases of thefirst symbol and the second symbol may be differently mapped.

In another aspect of the present disclosure, provided herein a basestation (BS) for transmitting a synchronization signal block (SSB) in awireless communication system, including a transceiver configured totransmit and receive a radio signal to and from a user equipment (UE),and a processor connected to the transceiver and configured to map atleast one SSB to a plurality of symbols and transmit the at least oneSSB in a first half-frame or a second half-frame included in a radioframe. A first SSB may be transmitted in the first half-frame and asecond SSB may be transmitted in the second half-frame. A signal of thesame type may be mapped to a first symbol included in a plurality ofsymbols to which the first SSB is mapped and a second symbol included ina plurality of symbols to which the second SSB is mapped. Phases of thefirst symbol and the second symbol may be differently mapped.

Advantageous Effects

According to the present disclosure, complexity of decoding for asynchronization signal block may be reduced by identifying a half-framein which the synchronization signal block is transmitted through a phaseof a symbol to which the synchronization signal block is mapped.

Effects according to the present disclosure are not limited to what hasbeen particularly described hereinabove and other advantages notdescribed herein will be more clearly understood by persons skilled inthe art from the following detailed description of the presentdisclosure.

DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating the control-plane and user-planearchitecture of radio interface protocols between a user equipment (UE)and an evolved UMTS terrestrial radio access network (E-UTRAN) inconformance to a 3rd generation partnership project (3GPP) radio accessnetwork standard.

FIG. 2 is a view illustrating physical channels and a general signaltransmission method using the physical channels in a 3GPP system.

FIG. 3 is a view illustrating a radio frame structure for transmitting asynchronization signal (SS) in a long term evolution (LTE) system.

FIG. 4 is a view illustrating an exemplary slot structure available innew radio access technology (NR).

FIG. 5 is a view illustrating exemplary connection schemes betweentransceiver units (TXRUs) and antenna elements.

FIG. 6 is a view abstractly illustrating a hybrid beamforming structurein terms of TXRUs and physical antennas.

FIG. 7 is a view illustrating beam sweeping for a synchronization signaland system information during downlink (DL) transmission.

FIG. 8 is a view illustrating an exemplary cell in an NR system.

FIGS. 9 to 12 are views for explaining a configuration method of asynchronization signal burst and a synchronization signal burst set.

FIGS. 13 to 18 are views illustrating methods of indexing asynchronization signal and methods of indicating a synchronizationsignal index, a system frame number (SFN), and a half-frame.

FIGS. 19 to 31 are views illustrating performance measurement resultsaccording to an embodiment of the present disclosure.

FIG. 32 is a view for explaining a method of acquiring half-frameboundary information according to an embodiment of the presentdisclosure.

FIGS. 33 and 34 are views for explaining embodiments for configuringbandwidths for a synchronization signal and a DL common channel.

FIG. 35 is a block diagram of communication devices according to anembodiment of the present disclosure.

BEST MODE FOR CARRYING OUT THE DISCLOSURE

The configuration, operation, and other features of the presentdisclosure will readily be understood with embodiments of the presentdisclosure described with reference to the attached drawings.Embodiments of the present disclosure as set forth herein are examplesin which the technical features of the present disclosure are applied toa 3rd generation partnership project (3GPP) system.

While embodiments of the present disclosure are described in the contextof long term evolution (LTE) and LTE-advanced (LTE-A) systems, they arepurely exemplary. Therefore, the embodiments of the present disclosureare applicable to any other communication system as long as the abovedefinitions are valid for the communication system.

The term, Base Station (BS) may be used to cover the meanings of termsincluding remote radio head (RRH), evolved Node B (eNB or eNode B),transmission point (TP), reception point (RP), relay, and so on.

The 3GPP communication standards define downlink (DL) physical channelscorresponding to resource elements (REs) carrying information originatedfrom a higher layer, and DL physical signals which are used in thephysical layer and correspond to REs which do not carry informationoriginated from a higher layer. For example, physical downlink sharedchannel (PDSCH), physical broadcast channel (PBCH), physical multicastchannel (PMCH), physical control format indicator channel (PCFICH),physical downlink control channel (PDCCH), and physical hybrid ARQindicator channel (PHICH) are defined as DL physical channels, andreference signals (RSs) and synchronization signals (SSs) are defined asDL physical signals. An RS, also called a pilot signal, is a signal witha predefined special waveform known to both a gNode B (gNB) and a UE.For example, cell specific RS, UE-specific RS (UE-RS), positioning RS(PRS), and channel state information RS (CSI-RS) are defined as DL RSs.The 3GPP LTE/LTE-A standards define uplink (UL) physical channelscorresponding to REs carrying information originated from a higherlayer, and UL physical signals which are used in the physical layer andcorrespond to REs which do not carry information originated from ahigher layer. For example, physical uplink shared channel (PUSCH),physical uplink control channel (PUCCH), and physical random accesschannel (PRACH) are defined as UL physical channels, and a demodulationreference signal (DMRS) for a UL control/data signal, and a soundingreference signal (SRS) used for UL channel measurement are defined as ULphysical signals.

In the present disclosure, the PDCCH/PCFICH/PHICH/PDSCH refers to a setof time-frequency resources or a set of REs, which carry downlinkcontrol information (DCI)/a control format indicator (CFI)/a DLacknowledgement/negative acknowledgement (ACK/NACK)/DL data. Further,the PUCCH/PUSCH/PRACH refers to a set of time-frequency resources or aset of REs, which carry UL control information (UCI)/UL data/a randomaccess signal. In the present disclosure, particularly a time-frequencyresource or an RE which is allocated to or belongs to thePDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH is referred to as a PDCCHRE/PCFICH RE/PHICH RE/PDSCH RE/PUCCH RE/PUSCH RE/PRACH RE or a PDCCHresource/PCFICH resource/PHICH resource/PDSCH resource/PUCCHresource/PUSCH resource/PRACH resource. Hereinbelow, if it is said thata UE transmits a PUCCH/PUSCH/PRACH, this means that UCI/UL data/a randomaccess signal is transmitted on or through the PUCCH/PUSCH/PRACH.Further, if it is said that a gNB transmits a PDCCH/PCFICH/PHICH/PDSCH,this means that DCI/control information is transmitted on or through thePDCCH/PCFICH/PHICH/PDSCH.

Hereinbelow, an orthogonal frequency division multiplexing (OFDM)symbol/carrier/subcarrier/RE to which a CRS/DMRS/CSI-RS/SRS/UE-RS isallocated to or for which the CRS/DMRS/CSI-RS/SRS/UE-RS is configured isreferred to as a CRS/DMRS/CSI-RS/SRS/UE-RS symbol/carrier/subcarrier/RE.For example, an OFDM symbol to which a tracking RS (TRS) is allocated orfor which the TRS is configured is referred to as a TRS symbol, asubcarrier to which a TRS is allocated or for which the TRS isconfigured is referred to as a TRS subcarrier, and an RE to which a TRSis allocated or for which the TRS is configured is referred to as a TRSRE. Further, a subframe configured to transmit a TRS is referred to as aTRS subframe. Further, a subframe carrying a broadcast signal isreferred to as a broadcast subframe or a PBCH subframe, and a subframecarrying a synchronization signal (SS) (e.g., a primary synchronizationsignal (PSS) and/or a secondary synchronization signal (SSS)) isreferred to as an SS subframe or a PSS/SSS subframe. An OFDMsymbol/subcarrier/RE to which a PSS/SSS is allocated or for which thePSS/SSS is configured is referred to as a PSS/SSS symbol/subcarrier/RE.

In the present disclosure, a CRS port, a UE-RS port, a CSI-RS port, anda TRS port refer to an antenna port configured to transmit a CRS, anantenna port configured to transmit a UE-RS, an antenna port configuredto transmit a CSI-RS, and an antenna port configured to transmit a TRS,respectively. Antenna port configured to transmit CRSs may bedistinguished from each other by the positions of REs occupied by theCRSs according to CRS ports, antenna ports configured to transmit UE-RSsmay be distinguished from each other by the positions of REs occupied bythe UE-RSs according to UE-RS ports, and antenna ports configured totransmit CSI-RSs may be distinguished from each other by the positionsof REs occupied by the CSI-RSs according to CSI-RS ports. Therefore, theterm CRS/UE-RS/CSI-RS/TRS port is also used to refer to a pattern of REsoccupied by a CRS/UE-RS/CSI-RS/TRS in a predetermined resource area.

FIG. 1 illustrates control-plane and user-plane protocol stacks in aradio interface protocol architecture conforming to a 3GPP wirelessaccess network standard between a user equipment (UE) and an evolvedUMTS terrestrial radio access network (E-UTRAN). The control plane is apath in which the UE and the E-UTRAN transmit control messages to managecalls, and the user plane is a path in which data generated from anapplication layer, for example, voice data or Internet packet data istransmitted.

A physical (PHY) layer at layer 1 (L1) provides information transferservice to its higher layer, a medium access control (MAC) layer. ThePHY layer is connected to the MAC layer via transport channels. Thetransport channels deliver data between the MAC layer and the PHY layer.Data is transmitted on physical channels between the PHY layers of atransmitter and a receiver. The physical channels use time and frequencyas radio resources. Specifically, the physical channels are modulated inorthogonal frequency division multiple access (OFDMA) for downlink (DL)and in single carrier frequency division multiple access (SC-FDMA) foruplink (UL).

The MAC layer at layer 2 (L2) provides service to its higher layer, aradio link control (RLC) layer via logical channels. The RLC layer at L2supports reliable data transmission. RLC functionality may beimplemented in a function block of the MAC layer. A packet dataconvergence protocol (PDCP) layer at L2 performs header compression toreduce the amount of unnecessary control information and thusefficiently transmit Internet protocol (IP) packets such as IP version 4(IPv4) or IP version 6 (IPv6) packets via an air interface having anarrow bandwidth.

A radio resource control (RRC) layer at the lowest part of layer 3 (orL3) is defined only on the control plane. The RRC layer controls logicalchannels, transport channels, and physical channels in relation toconfiguration, reconfiguration, and release of radio bearers. A radiobearer refers to a service provided at L2, for data transmission betweenthe UE and the E-UTRAN. For this purpose, the RRC layers of the UE andthe E-UTRAN exchange RRC messages with each other. If an RRC connectionis established between the UE and the E-UTRAN, the UE is in RRCConnected mode and otherwise, the UE is in RRC Idle mode. A Non-AccessStratum (NAS) layer above the RRC layer performs functions includingsession management and mobility management.

DL transport channels used to deliver data from the E-UTRAN to UEsinclude a broadcast channel (BCH) carrying system information, a pagingchannel (PCH) carrying a paging message, and a shared channel (SCH)carrying user traffic or a control message. DL multicast traffic orcontrol messages or DL broadcast traffic or control messages may betransmitted on a DL SCH or a separately defined DL multicast channel(MCH). UL transport channels used to deliver data from a UE to theE-UTRAN include a random access channel (RACH) carrying an initialcontrol message and a UL SCH carrying user traffic or a control message.Logical channels that are defined above transport channels and mapped tothe transport channels include a broadcast control channel (BCCH), apaging control channel (PCCH), a Common Control Channel (CCCH), amulticast control channel (MCCH), a multicast traffic channel (MTCH),etc.

FIG. 2 illustrates physical channels and a general method fortransmitting signals on the physical channels in the 3GPP system.

Referring to FIG. 2, when a UE is powered on or enters a new cell, theUE performs initial cell search (S201). The initial cell search involvesacquisition of synchronization to an eNB. Specifically, the UEsynchronizes its timing to the eNB and acquires a cell identifier (ID)and other information by receiving a primary synchronization channel(P-SCH) and a secondary synchronization channel (S-SCH) from the eNB.Then the UE may acquire information broadcast in the cell by receiving aphysical broadcast channel (PBCH) from the eNB. During the initial cellsearch, the UE may monitor a DL channel state by receiving a DownLinkreference signal (DL RS).

After the initial cell search, the UE may acquire detailed systeminformation by receiving a physical downlink control channel (PDCCH) andreceiving a physical downlink shared channel (PDSCH) based oninformation included in the PDCCH (S202).

If the UE initially accesses the eNB or has no radio resources forsignal transmission to the eNB, the UE may perform a random accessprocedure with the eNB (S203 to S206). In the random access procedure,the UE may transmit a predetermined sequence as a preamble on a physicalrandom access channel (PRACH) (S203 and S205) and may receive a responsemessage to the preamble on a PDCCH and a PDSCH associated with the PDCCH(S204 and S206). In the case of a contention-based RACH, the UE mayadditionally perform a contention resolution procedure.

After the above procedure, the UE may receive a PDCCH and/or a PDSCHfrom the eNB (S207) and transmit a physical uplink shared channel(PUSCH) and/or a physical uplink control channel (PUCCH) to the eNB(S208), which is a general DL and UL signal transmission procedure.Particularly, the UE receives downlink control information (DCI) on aPDCCH. Herein, the DCI includes control information such as resourceallocation information for the UE. Different DCI formats are definedaccording to different usages of DCI.

Control information that the UE transmits to the eNB on the UL orreceives from the eNB on the DL includes a DL/UL acknowledgment/negativeacknowledgment (ACK/NACK) signal, a channel quality indicator (CQI), aprecoding matrix index (PMI), a rank indicator (RI), etc. In the 3GPPLTE system, the UE may transmit control information such as a CQI, aPMI, an RI, etc. on a PUSCH and/or a PUCCH.

FIG. 3 is a diagram illustrating a radio frame structure fortransmitting a synchronization signal (SS) in LTE system. In particular,FIG. 3 illustrates a radio frame structure for transmitting asynchronization signal and PBCH in frequency division duplex (FDD). FIG.3(a) shows positions at which the SS and the PBCH are transmitted in aradio frame configured by a normal cyclic prefix (CP) and FIG. 3(b)shows positions at which the SS and the PBCH are transmitted in a radioframe configured by an extended CP.

An SS will be described in more detail with reference to FIG. 3. An SSis categorized into a primary synchronization signal (PSS) and asecondary synchronization signal (SSS). The PSS is used to acquiretime-domain synchronization such as OFDM symbol synchronization, slotsynchronization, etc. and/or frequency-domain synchronization. And, theSSS is used to acquire frame synchronization, a cell group ID, and/or aCP configuration of a cell (i.e. information indicating whether to anormal CP or an extended is used). Referring to FIG. 4, a PSS and an SSSare transmitted through two OFDM symbols in each radio frame.Particularly, the SS is transmitted in first slot in each of subframe 0and subframe 5 in consideration of a GSM (Global System for Mobilecommunication) frame length of 4.6 ms for facilitation of inter-radioaccess technology (inter-RAT) measurement. Especially, the PSS istransmitted in a last OFDM symbol in each of the first slot of subframe0 and the first slot of subframe 5. And, the SSS is transmitted in asecond to last OFDM symbol in each of the first slot of subframe 0 andthe first slot of subframe 5. Boundaries of a corresponding radio framemay be detected through the SSS. The PSS is transmitted in the last OFDMsymbol of the corresponding slot and the SSS is transmitted in the OFDMsymbol immediately before the OFDM symbol in which the PSS istransmitted. According to a transmission diversity scheme for the SS,only a single antenna port is used. However, the transmission diversityscheme for the SS standards is not separately defined in the currentstandard.

Referring to FIG. 3, by detecting the PSS, a UE may know that acorresponding subframe is one of subframe 0 and subframe 5 since the PSSis transmitted every 5 ms but the UE cannot know whether the subframe issubframe 0 or subframe 5. That is, frame synchronization cannot beobtained only from the PSS. The UE detects the boundaries of the radioframe in a manner of detecting an SSS which is transmitted twice in oneradio frame with different sequences.

Having demodulated a DL signal by performing a cell search procedureusing the PSS/SSS and determined time and frequency parameters necessaryto perform UL signal transmission at an accurate time, a UE cancommunicate with an eNB only after obtaining system informationnecessary for a system configuration of the UE from the eNB.

The system information is configured with a master information block(MIB) and system information blocks (SIBs). Each SIB includes a set offunctionally related parameters and is categorized into an MIB, SIB Type1 (SIB1), SIB Type 2 (SIB2), and SIB3 to SIB8 according to the includedparameters.

The MIB includes most frequently transmitted parameters which areessential for a UE to initially access a network served by an eNB. TheUE may receive the MIB through a broadcast channel (e.g. a PBCH). TheMIB includes a downlink system bandwidth (DL BW), a PHICH configuration,and a system frame number (SFN). Thus, the UE can explicitly knowinformation on the DL BW, SFN, and PHICH configuration by receiving thePBCH. On the other hand, the UE may implicitly know information on thenumber of transmission antenna ports of the eNB. The information on thenumber of the transmission antennas of the eNB is implicitly signaled bymasking (e.g. XOR operation) a sequence corresponding to the number ofthe transmission antennas to 16-bit cyclic redundancy check (CRC) usedin detecting an error of the PBCH.

The SIB1 includes not only information on time-domain scheduling forother SIBs but also parameters necessary to determine whether a specificcell is suitable in cell selection. The UE receives the SIB1 viabroadcast signaling or dedicated signaling.

A DL carrier frequency and a corresponding system bandwidth can beobtained by MIB carried by PBCH. A UL carrier frequency and acorresponding system bandwidth can be obtained through systeminformation corresponding to a DL signal. Having received the MIB, ifthere is no valid system information stored in a corresponding cell, aUE applies a value of a DL BW included in the MIB to a UL bandwidthuntil system information block type 2 (SystemInformationBlockType2,SIB2) is received. For example, if the UE obtains the SIB2, the UE isable to identify the entire UL system bandwidth capable of being usedfor UL transmission through UL-carrier frequency and UL-bandwidthinformation included in the SIB2.

In the frequency domain, PSS/SSS and PBCH are transmitted irrespectiveof an actual system bandwidth in total 6 RBs, i.e., 3 RBs in the leftside and 3 RBs in the right side with reference to a DC subcarrierwithin a corresponding OFDM symbol. In other words, the PSS/SSS and thePBCH are transmitted only in 72 subcarriers. Therefore, a UE isconfigured to detect or decode the SS and the PBCH irrespective of adownlink transmission bandwidth configured for the UE.

Having completed the initial cell search, the UE can perform a randomaccess procedure to complete the accessing the eNB. To this end, the UEtransmits a preamble via PRACH (physical random access channel) and canreceive a response message via PDCCH and PDSCH in response to thepreamble. In case of contention based random access, it may transmitadditional PRACH and perform a contention resolution procedure such asPDCCH and PDSCH corresponding to the PDCCH.

Having performed the abovementioned procedure, the UE can performPDCCH/PDSCH reception and PUSCH/PUCCH transmission as a general UL/DLsignal transmission procedure.

The random access procedure is also referred to as a random accesschannel (RACH) procedure. The random access procedure is used forvarious usages including initial access, UL synchronization adjustment,resource allocation, handover, and the like. The random access procedureis categorized into a contention-based procedure and a dedicated (i.e.,non-contention-based) procedure. In general, the contention-based randomaccess procedure is used for performing initial access. On the otherhand, the dedicated random access procedure is restrictively used forperforming handover, and the like. When the contention-based randomaccess procedure is performed, a UE randomly selects a RACH preamblesequence. Hence, a plurality of UEs can transmit the same RACH preamblesequence at the same time. As a result, a contention resolutionprocedure is required thereafter. On the contrary, when the dedicatedrandom access procedure is performed, the UE uses an RACH preamblesequence dedicatedly allocated to the UE by an eNB. Hence, the UE canperform the random access procedure without a collision with a differentUE.

The contention-based random access procedure includes 4 steps describedin the following. Messages transmitted via the 4 steps can berespectively referred to as message (Msg) 1 to 4 in the presentdisclosure.

-   -   Step 1: RACH preamble (via PRACH) (UE to eNB)    -   Step 2: Random access response (RAR) (via PDCCH and PDSCH (eNB        to)    -   Step 3: Layer 2/Layer 3 message (via PUSCH) (UE to eNB)    -   Step 4: Contention resolution message (eNB to UE)

On the other hand, the dedicated random access procedure includes 3steps described in the following. Messages transmitted via the 3 stepscan be respectively referred to as message (Msg) 0 to 2 in the presentdisclosure. It may also perform uplink transmission (i.e., step 3)corresponding to PAR as a part of the ransom access procedure. Thededicated random access procedure can be triggered using PDCCH(hereinafter, PDCCH order) which is used for an eNB to indicatetransmission of an RACH preamble.

-   -   Step 0: RACH preamble assignment via dedicated signaling (eNB to        UE)    -   Step 1: RACH preamble (via PRACH) (UE to eNB)    -   Step 2: Random access response (RAR) (via PDCCH and PDSCH) (eNB        to UE)

After the RACH preamble is transmitted, the UE attempts to receive arandom access response (RAR) in a preconfigured time window.Specifically, the UE attempts to detect PDCCH (hereinafter, RA-RNTIPDCCH) (e.g., a CRC masked with RA-RNTI in PDCCH) having RA-RNTI (randomaccess RNTI) in a time window. If the RA-RNTI PDCCH is detected, the UEchecks whether or not there is a RAR for the UE in PDSCH correspondingto the RA-RNTI PDCCH. The RAR includes timing advance (TA) informationindicating timing offset information for UL synchronization, UL resourceallocation information (UL grant information), a temporary UE identifier(e.g., temporary cell-RNTI, TC-RNTI), and the like. The UE can performUL transmission (e.g., message 3) according to the resource allocationinformation and the TA value included in the RAR. HARQ is applied to ULtransmission corresponding to the RAR. In particular, the UE can receivereception response information (e.g., PHICH) corresponding to themessage 3 after the message 3 is transmitted.

A random access preamble (i.e. RACH preamble) consists of a cyclicprefix of a length of TCP and a sequence part of a length of TSEQ. TheTCP and the TSEQ depend on a frame structure and a random accessconfiguration. A preamble format is controlled by higher layer. The RACHpreamble is transmitted in a UL subframe. Transmission of the randomaccess preamble is restricted to a specific time resource and afrequency resource. The resources are referred to as PRACH resources. Inorder to match an index 0 with a PRB and a subframe of a lower number ina radio frame, the PRACH resources are numbered in an ascending order ofPRBs in subframe numbers in the radio frame and frequency domain. Randomaccess resources are defined according to a PRACH configuration index(refer to 3GPP TS 36.211 standard document). The RACH configurationindex is provided by a higher layer signal (transmitted by an eNB).

In the LTE/LTE-A system, a subcarrier spacing for a random accesspreamble (i.e., RACH preamble) is regulated by 1.25 kHz and 7.5 kHz forpreamble formats 0 to 3 and a preamble format 4, respectively (refer to3GPP TS 36.211).

<OFDM Numerology>

A New RAT system adopts an OFDM transmission scheme or a transmissionscheme similar to the OFDM transmission scheme. The New RAT system mayuse different OFDM parameters from LTE OFDM parameters. Or the New RATsystem may follow the numerology of legacy LTE/LTE-A but have a largersystem bandwidth (e.g., 100 MHz). Or one cell may support a plurality ofnumerologies. That is, UEs operating with different numerologies mayco-exist within one cell.

<Subframe Structure>

In the 3GPP LTE/LTE-A system, a radio frame is 10 ms (307200 Ts) long,including 10 equal-size subframes (SFs). The 10 SFs of one radio framemay be assigned numbers. Ts represents a sampling time and is expressedas Ts=1/(2048*15 kHz). Each SF is 1 ms, including two slots. The 20slots of one radio frame may be sequentially numbered from 0 to 19. Eachslot has a length of 0.5 ms. A time taken to transmit one SF is definedas a transmission time interval (TTI). A time resource may bedistinguished by a radio frame number (or radio frame index), an SFnumber (or SF index), a slot number (or slot index), and so on. A TTIrefers to an interval in which data may be scheduled. In the currentLTE/LTE-A system, for example, there is a UL grant or DL granttransmission opportunity every 1 ms, without a plurality of UL/DL grantopportunities for a shorter time than 1 ms. Accordingly, a TTI is 1 msin the legacy LTE/LTE-A system.

FIG. 4 illustrates an exemplary slot structure available in the newradio access technology (NR).

To minimize a data transmission delay, a slot structure in which acontrol channel and a data channel are multiplexed in time divisionmultiplexing (TDM) is considered in 5th generation (5G) NR.

In FIG. 4, an area marked with slanted lines represents a transmissionregion of a DL control channel (e.g., PDCCH) carrying DCI, and a blackpart represents a transmission region of a UL control channel (e.g.,PUCCH) carrying UCI. DCI is control information that a gNB transmits toa UE, and may include information about a cell configuration that a UEshould know, DL-specific information such as DL scheduling, andUL-specific information such as a UL grant. Further, UCI is controlinformation that a UE transmits to a gNB. The UCI may include an HARQACK/NACK report for DL data, a CSI report for a DL channel state, ascheduling request (SR), and so on.

In FIG. 4, symbols with symbol index 1 to symbol index 12 may be usedfor transmission of a physical channel (e.g., PDSCH) carrying DL data,and also for transmission of a physical channel (e.g., PUSCH) carryingUL data. According to the slot structure illustrated in FIG. 2, as DLtransmission and UL transmission take place sequentially in one slot,transmission/reception of DL data and reception/transmission of a ULACK/NACK for the DL data may be performed in the one slot. As aconsequence, when an error is generated during data transmission, a timetaken for a data retransmission may be reduced, thereby minimizing thedelay of a final data transmission.

In this slot structure, a time gap is required to allow a gNB and a UEto switch from a transmission mode to a reception mode or from thereception mode to the transmission mode. For the switching between thetransmission mode and the reception mode, some OFDM symbol correspondingto a DL-to-UL switching time is configured as a guard period (GP) in theslot structure.

In the legacy LTE/LTE-A system, a DL control channel is multiplexed witha data channel in TDM, and a control channel, PDCCH is transmitteddistributed across a total system band. In NR, however, it is expectedthat the bandwidth of one system will be at least about 100 MHz, whichmakes it inviable to transmit a control channel across a total band. Ifa UE monitors the total band to receive a DL control channel, for datatransmission/reception, this may increase the battery consumption of theUE and decrease efficiency. Therefore, a DL control channel may betransmitted localized or distributed in some frequency band within asystem band, that is, a channel band in the present disclosure.

In the NR system, a basic transmission unit is a slot. A slot durationincludes 14 symbols each having a normal cyclic prefix (CP), or 12symbols each having an extended CP. Further, a slot is scaled in time bya function of a used subcarrier spacing. That is, as the subcarrierspacing increases, the length of a slot decreases. For example, given 14symbols per slot, if the number of slots in a 10-ms frame is 10 for asubcarrier spacing of 15 kHz, the number of slots is 20 for a subcarrierspacing of 30 kHz, and 40 for a subcarrier spacing of 60 kHz. As thesubcarrier spacing increases, the length of an OFDM symbol decreases.The number of OFDM symbols per slot is different depending on the normalCP or the extended CP, and does not change according to a subcarrierspacing. The basic time unit for LTE, Ts is defined as 1/(15000*2048)seconds, in consideration of the basic 15-kHz subcarrier spacing and amaximum FFT size of 2048. Ts is also a sampling time for the 15-kHzsubcarrier spacing. In the NR system, many other subcarrier spacingsthan 15 kHz are available, and since a subcarrier spacing is inverselyproportional to a corresponding time length, an actual sampling time Tscorresponding to subcarrier spacings larger than 15 kHz becomes shorterthan 1/(15000*2048) seconds. For example, the actual sampling time forthe subcarrier spacings of 30 kHz, 60 kHz, and 120 kHz may be1/(2*15000*2048) seconds, 1/(4*15000*2048) seconds, and 1/(8*15000*2048)seconds, respectively.

<Analog Beamforming>

For a 5G mobile communication system under discussion, a technique ofusing an ultra-high frequency band, that is, a millimeter frequency bandat or above 6 GHz is considered in order to transmit data to a pluralityof users at a high transmission rate in a wide frequency band. The 3GPPcalls this technique NR, and thus a 5G mobile communication system willbe referred to as an NR system in the present disclosure. However, themillimeter frequency band has the frequency property that a signal isattenuated too rapidly according to a distance due to the use of toohigh a frequency band. Accordingly, the NR system using a frequency bandat or above at least 6 GHz employs a narrow beam transmission scheme inwhich a signal is transmitted with concentrated energy in a specificdirection, not omni-directionally, to thereby compensate for the rapidpropagation attenuation and thus overcome the decrease of coveragecaused by the rapid propagation attenuation. However, if a service isprovided by using only one narrow beam, the service coverage of one gNBbecomes narrow, and thus the gNB provides a service in a wideband bycollecting a plurality of narrow beams.

As a wavelength becomes short in the millimeter frequency band, that is,millimeter wave (mmW) band, it is possible to install a plurality ofantenna elements in the same area. For example, a total of 100 antennaelements may be installed at (wavelength) intervals of 0.5 lamda in a30-GHz band with a wavelength of about lcm in a two-dimensional (2D)array on a 5 by 5 cm panel. Therefore, it is considered to increasecoverage or throughput by increasing a beamforming gain through use of aplurality of antenna elements in mmW.

To form a narrow beam in the millimeter frequency band, a beamformingscheme is mainly considered, in which a gNB or a UE transmits the samesignals with appropriate phase differences through multiple antennas, tothereby increase energy only in a specific direction. Such beamformingschemes include digital beamforming for generating a phase differencebetween digital baseband signals, analog beamforming for generating aphase difference between modulated analog signals by using a time delay(i.e., a cyclic shift), and hybrid beamforming using both digitalbeamforming and analog beamforming. If a TXRU is provided per antennaelement to enable control of transmission power and a phase per antenna,independent beamforming per frequency resource is possible. However,installation of TXRUs for all of about 100 antenna elements is noteffective in terms of cost. That is, to compensate for rapid propagationattenuation in the millimeter frequency band, multiple antennas shouldbe used, and digital beamforming requires as many RF components (e.g.,digital to analog converters (DACs), mixers, power amplifiers, andlinear amplifiers) as the number of antennas. Accordingly,implementation of digital beamforming in the millimeter frequency bandfaces the problem of increased cost of communication devices. Therefore,in the case where a large number of antennas are required as in themillimeter frequency band, analog beamforming or hybrid beamforming isconsidered. In analog beamforming, a plurality of antenna elements aremapped to one TXRU, and the direction of a beam is controlled by ananalog phase shifter. A shortcoming with this analog beamforming schemeis that frequency selective beamforming (BF) cannot be provided becauseonly one beam direction can be produced in a total band. Hybrid BFstands between digital BF and analog BF, in which B TXRUs fewer than Qantenna elements are used. In hybrid BF, the directions of beamstransmittable at the same time is limited to or below B although thenumber of beam directions is different according to connections betweenB TXRUs and Q antenna elements.

FIG. 5 is a view illustrating exemplary connection schemes between TXRUsand antenna elements.

(a) of FIG. 5 illustrates connection between a TXRU and a sub-array. Inthis case, an antenna element is connected only to one TXRU. Incontrast, (b) of FIG. 5 illustrates connection between a TXRU and allantenna elements. In this case, an antenna element is connected to allTXRUs. In FIG. 5, W represents a phase vector subjected tomultiplication in an analog phase shifter. That is, a direction ofanalog beamforming is determined by W. Herein, CSI-RS antenna ports maybe mapped to TXRUs in a one-to-one or one-to-many correspondence.

As mentioned before, since a digital baseband signal to be transmittedor a received digital baseband signal is subjected to a signal processin digital beamforming, a signal may be transmitted or received in orfrom a plurality of directions on multiple beams. In contrast, in analogbeamforming, an analog signal to be transmitted or a received analogsignal is subjected to beamforming in a modulated state. Thus, signalscannot be transmitted or received simultaneously in or from a pluralityof directions beyond the coverage of one beam. A gNB generallycommunicates with multiple users at the same time, relying on thewideband transmission or multiple antenna property. If the gNB usesanalog BF or hybrid BF and forms an analog beam in one beam direction,the gNB has no way other than to communicate only with users covered inthe same analog beam direction in view of the nature of analog BF. Alater-described RACH resource allocation and gNB resource utilizationscheme according to the present disclosure is proposed by reflectinglimitations caused by the nature of analog BF or hybrid BF.

<Hybrid Analog Beamforming>

FIG. 6 abstractly illustrates a hybrid beamforming structure in terms ofTXRUs and physical antennas.

For the case where multiple antennas are used, hybrid BF with digital BFand analog BF in combination has emerged. Analog BF (or RF BF) is anoperation of performing precoding (or combining) in an RF unit. Due toprecoding (combining) in each of a baseband unit and an RF unit, hybridBF offers the benefit of performance close to the performance of digitalBF, while reducing the number of RF chains and the number of DACs (oranalog to digital converters (ADCs). For the convenience' sake, a hybridBF structure may be represented by N TXRUs and M physical antennas.Digital BF for L data layers to be transmitted by a transmission end maybe represented as an N-by-N matrix, and then N converted digital signalsare converted to analog signals through TXRUs and subjected to analog BFrepresented as an M-by-N matrix. In FIG. 6, the number of digital beamsis L, and the number of analog beams is N. Further, it is considered inthe NR system that a gNB is configured to change analog BF on a symbolbasis so as to more efficiently support BF for a UE located in aspecific area. Further, when one antenna panel is defined by N TXRUs andM RF antennas, introduction of a plurality of antenna panels to whichindependent hybrid BF is applicable is also considered. As such, in thecase where a gNB uses a plurality of analog beams, a different analogbeam may be preferred for signal reception at each UE. Therefore, a beamsweeping operation is under consideration, in which for at least an SS,system information, and paging, a gNB changes a plurality of analogbeams on a symbol basis in a specific slot or SF to allow all UEs tohave reception opportunities.

FIG. 7 is a view illustrating beam sweeping for an SS and systeminformation during DL transmission. In FIG. 7, physical resources or aphysical channel which broadcasts system information of the New RATsystem is referred to as an xPBCH. Analog beams from different antennapanels may be transmitted simultaneously in one symbol, and introductionof a beam reference signal (BRS) transmitted for a single analog beamcorresponding to a specific antenna panel as illustrated in FIG. 7 isunder discussion in order to measure a channel per analog beam. BRSs maybe defined for a plurality of antenna ports, and each antenna port ofthe BRSs may correspond to a single analog beam. Unlike the BRSs, the SSor the xPBCH may be transmitted for all analog beams included in ananalog beam group so that any UE may receive the SS or the xPBCHsuccessfully.

FIG. 8 is a view illustrating an exemplary cell in the NR system.

Referring to FIG. 8, compared to a wireless communication system such aslegacy LTE in which one eNB forms one cell, configuration of one cell bya plurality of TRPs is under discussion in the NR system. If a pluralityof TRPs form one cell, even though a TRP serving a UE is changed,seamless communication is advantageously possible, thereby facilitatingmobility management for UEs.

Compared to the LTE/LTE-A system in which a PSS/SSS is transmittedomni-directionally, a method for transmitting a signal such as aPSS/SSS/PBCH through BF performed by sequentially switching a beamdirection to all directions at a gNB applying mmWave is considered. Thesignal transmission/reception performed by switching a beam direction isreferred to as beam sweeping or beam scanning. In the presentdisclosure, “beam sweeping” is a behavior of a transmission side, and“beam scanning” is a behavior of a reception side. For example, if up toN beam directions are available to the gNB, the gNB transmits a signalsuch as a PSS/SSS/PBCH in the N beam directions. That is, the gNBtransmits an SS such as the PSS/SSS/PBCH in each direction by sweeping abeam in directions available to or supported by the gNB. Or if the gNBis capable of forming N beams, the beams may be grouped, and thePSS/SSS/PBCH may be transmitted/received on a group basis. One beamgroup includes one or more beams. Signals such as the PSS/SSS/PBCHtransmitted in the same direction may be defined as one SS block (SSB),and a plurality of SSBs may exist in one cell. If a plurality of SSBsexist, an SSB index may be used to identify each SSB. For example, ifthe PSS/SSS/PBCH is transmitted in 10 beam directions in one system, thePSS/SSS/PBCH transmitted in the same direction may form an SSB, and itmay be understood that 10 SSBs exist in the system. In the presentdisclosure, a beam index may be interpreted as an SSB index.

Hereinafter, a method of generating an SS and a method of indicatingtime indexes such as an SS index and a half-frame index according to anembodiment of the present disclosure will be described.

Prior to a description of the present disclosure, a “high-order bit” ora “most significant bit (MSB)” represented in the present disclosure mayimply a left bit in the arrangement of information bits in which ahighest-digit number is placed at a rightmost position. That is, in thearrangement of information bits in which a highest-digit number isplaced at a leftmost position, the “high-order bit” or the “MSB” may beinterpreted as having the same meaning as a least significant bit (LSB),which is a bit giving a units value for determining whether a valueindicated by the information bits is even or odd of an integer.

Similarly, a “low-order bit” or an “LSB” may imply a right bit in thearrangement of information bits in which a highest-digit number isplaced at a rightmost position. In other words, in the arrangement ofinformation bits in which a highest-digit number is placed at a leftmostposition, the “low-order bit” or the “LSB” may be interpreted as havingthe same meaning as the MSB.

For example, in the description of the disclosure which will be givenlater, there is an expression of “the UE acquires high-order N bits(e.g., S0, S1, and S2) of SFN information and acquires the other (10-N)bits (e.g., S3 to S9) of the SFN information from PBCH content, therebyconfiguring a total of 10 bits of the SFN information.

In this case, in an arrangement in which a highest-digit number isplaced at a rightmost position in an order of an information bit stream,i.e., in an information bit stream configured as (S0 S1 S2 S3 . . . S9),“high-order N bits” means left N bits (e.g., S0 S1 S2) and “the other(10-N) bits” means right (10-N) bits (e.g., S3 to S9). This may beexpressed as follows using an LSB and an MSB. In an information bitstream represented in order of (S9 S8 S7 . . . S1 S0), a bit steam usingN LSBs may be expressed in order of N bits (e.g., S2 S1 S0) and a bitstream corresponding to “the other (10-N) bits (e.g., S3 to S9)” using(10-N) MSBs may be expressed in order of (S9 S8 S7 . . . S3).

1. SSB Configuration

If a PSS is positioned at a front part of an SSB when subcarrierspacings of 120 kHz and 240 kHz are used, a problem may arise in anautomatic gain control (AGC) operation of a UE. That is, in thesubcarrier spacings of 120 kHz and 240 kHz, an NR-PSS may not becorrectly detected due to the AGC operation. Therefore, modification ofan SSB configuration may be considered as in the following twoembodiments.

(Method 1) PBCH-PSS-PBCH-SSS

(Method 2) PBCH-PSS-PBCH-SSS-PBCH

Namely, a PBCH symbol may be positioned at a start part of the SSB andmay be used as a dummy symbol for the AGC operation so that the AGCoperation of the UE may be smoothly performed.

2. SS Burst Set Configuration

FIG. 9 illustrates an SS burst set configuration when subcarrierspacings for arranging an SSB are 120 kHz and 240 kHz. Referring to FIG.9, the SS burst set is configured with a predetermined duration beingemptied in units of 4 SS bursts when the subcarrier spacings are 120 kHzand 240 kHz. That is, the SSB is arranged in units of 0.5 ms with asymbol duration for UL transmission of 0.125 ms being emptied.

However, in the frequency range above 60 GHz, a subcarrier spacing of 60kHz may be used for data transmission. That is, as illustrated in FIG.10, in NR, a subcarrier spacing of 60 kHz for data transmission and asubcarrier spacing of 120 kHz or 240 kHz for SSB transmission may bemultiplexed.

Meanwhile, referring to a part indicated by a box in FIG. 10, while theSSB of the 120-kHz subcarrier spacing and data of the 60-kHz subcarrierspacing are multiplexed, it may be appreciated that collision or overlapoccurs between an SSB of the 120-kHz subcarrier spacing and a GP and aDL control region of the 60-kHz subcarrier spacing. Since it isdesirable that collision between the SSB and the DL/UL control region beavoided if possible, configurations of the SS burst and the SS burst setneed to be modified.

The present disclosure proposes two embodiments as a modification of theSS burst configuration to solve the above problem.

In the first embodiment, positions of SS burst format 1 and SS burstformat 2 are changed as illustrated in FIG. 11. That is, SS burst format1 and SS burst format 2 in the box of FIG. 10 interchange so as not togenerate collision between the SSB and the DL/UL control region. Inother words, SS burst format 1 is located at a front part of a slot ofthe 60-kHz subcarrier spacing and SS burst format 2 is located at a rearpart of the slot of the 60-kHz subcarrier spacing.

The above-described embodiment may be summarized as follows.

1) 120-KHz Subcarrier Spacing

The first OFDM symbols of candidate SS/PBCH blocks have indexes {4, 8,16, 20, 32, 36, 44, 48}+70*n. For carrier frequencies higher than 6 GHz,n=0, 2, 4, 6.

The first OFDM symbols of the candidate SS/PBCH blocks have indexes {2,6, 18, 22, 30, 34, 46, 50}+70*n. For carrier frequencies higher than 6GHz, n=1, 3, 5, 7.

2) 240-KHz Subcarrier Spacing

The first OFDM symbols of the candidate SS/PBCH blocks have indexes {8,12, 16, 20, 32, 36, 40, 44, 64, 68, 72, 76, 88, 92, 96, 100}+140*n. Forcarrier frequencies higher than 6 GHz, n=0, 2.

The first OFDM symbols of the candidate SS/PBCH blocks have indexes {4,8, 12, 16, 36, 40, 44, 48, 60, 64, 68, 72, 92, 96, 100, 104}+140*n. Forcarrier frequencies higher than 6 GHz, n=1, 3.

In the second embodiment, the SS burst set configuration is changed asillustrated in FIG. 12. That is, an SS burst set may be configured toalign, i.e., match, a start boundary of the SS burst set and a startboundary of a slot of a 60-kHz subcarrier spacing.

Specifically, an SS burst is configured by SSBs which are locallyarranged during 1 ms. Therefore, during 1 ms, an SS burst of a 120-kHzsubcarrier spacing includes 16 SSBs and an SS burst of a 240-kHzsubcarrier spacing includes 32 SSBs. If the SS burst is configured inthis way, one slot is allocated, as a gap, between SS bursts based onthe 60-kHz subcarrier spacing.

The above-described second embodiment is summarized as follows.

1) 120-KHz Subcarrier Spacing

The first OFDM symbols of the candidate SS/PBCH blocks have indexes {4,8, 16, 20}+28*n. For carrier frequencies higher than 6 GHz, n=0, 1, 2,3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18.

2) 240 KHz Subcarrier Spacing

The first OFDM symbols of the candidate SS/PBCH blocks have indexes {8,12, 16, 20, 32, 36, 40, 44}+56*n. For carrier frequencies higher than 6GHz, n=0, 1, 2, 3, 5, 6, 7, 8.

3. Indication of Actually Transmitted SS/PBCH Block within 5-ms Duration

Meanwhile, the number of candidates for SSB transmission may be limitedaccording to a network environment. For example, the number ofcandidates may differ according to a subcarrier spacing with which anSSB is disposed. In this case, the position of an actually transmittedSSB may be indicated to a connected/idle mode UE. An actuallytransmitted SS/PBCH block indication indicating the position of anactually transmitted SSB may be used for a serving cell for the purposeof resource utilization, e.g., rate matching, and may be used for aneighbor cell for the purpose of measurement associated with acorresponding resource.

In association with the serving cell, if the UE is capable of accuratelyrecognizing an SSB which is not transmitted, the UE may identify thatthe UE can receive other information such as paging or data through acandidate resource of the SSB which is not transmitted. For flexibilityof such a resource, it is necessary to accurately indicate an SSB whichis actually transmitted in a serving cell.

That is, since other information such as paging or data cannot bereceived in a resource in which the SSB is transmitted, the UE needs torecognize an SSB candidate corresponding to the SSB which is notactually transmitted in order to raise resource use efficiency byreceiving other data or other signals through the SSB which is notactually transmitted.

Therefore, in order to accurately indicate the SSB which is actuallytransmitted in the serving cell, full bitmap information of 4, 8, or 64bits is needed. In this case, the size of bits included in a bitmap maybe determined according to the maximum number of SSBs which can bemaximally transmitted in each frequency range. For example, to indicatethe SSB which is actually transmitted in a duration of 5 ms, 8 bits areneeded in the frequency range from 3 GHz to 6 GHz and 64 bits are neededin the frequency range above 6 GHz.

Bits for the SSB which is actually transmitted in the serving cell maybe defined in remaining system information (RMSI) or other systeminformation (OSI). The RMSI/OSI includes configuration information fordata or paging. Since the actually transmitted SS/PBCH block indicationis associated with a configuration for a DL resource, it may beconcluded that the RMSI/OSI includes SSB information.

Meanwhile, the actually transmitted SS/PBCH block indication of theneighbor cell may be required for the purpose of measurement of theneighbor cell. That is, time synchronization information of the neighborcell needs to be acquired for measurement of the neighbor cell. When anNR system is designed to allow asynchronous transmission between TRPs,even if the time synchronization information of the neighbor cell isindicated, accuracy of the information may differ according to asituation. Therefore, when the time information of the neighbor cell isindicated, it is necessary to determine the unit of the time informationas valid information for the UE even under the assumption thatasynchronous transmission is performed between TRPs.

Herein, if there are many listed cells, a full bitmap type of indicationmay excessively increase signaling overhead. Hence, in order to reducesignaling overhead, a variably compressed type of indication may beconsidered. Meanwhile, even an indication for an SSB that a serving celltransmits may consider a compressed type for the purpose of reducingsignaling overhead as well as for the purpose of neighbor cellmeasurement. In other words, an SSB indication described below may beused to indicate an actually transmitted SSB in the neighbor cell andthe serving cell. In addition, according to the above description,although an SS burst may imply a bundle of SSBs included in one slotaccording to each subcarrier, the SS burst may imply, only inembodiments described below, an SSB group obtained by grouping apredetermined number of SSBs regardless of the slot.

One of the embodiments will now be described with reference to FIG. 13.Assuming that the SS burst includes 8 SSBs, a total of 8 SS bursts maybe present in a band above 64 GHz in which 64 SSBs may be positioned.

In this case, SSBs are grouped into SS bursts to compress a total bitmapof 64 bits. Instead of 64-bit bitmap information, 8-bit informationindicating SS bursts including actually transmitted SSBs may be used. Ifthe 8-bit bitmap information indicates SS burst #0, then SS burst #0 mayinclude one or more actually transmitted SSBs.

Herein, additional information for additionally indicating the number ofSSBs transmitted per SS burst to the UE may be considered. As many SSBsas the number of SSBs indicated by the additional information may belocally present in each SS burst.

Therefore, the UE may estimate actually transmitted SSBs by combiningthe number of actually transmitted SSBs per SS burst, indicated by theadditional information, and the bitmap for indicating an SS burstincluding actually transmitted SSBs.

For example, an indication example of Table 1 below may be assumed.

TABLE 1 The number of 8 bit bitmap actually transmitted (SS/PBCH SS/PBCHblocks per burst unit) SS/PBCH burst unit Full bitmap 1 1 0 0 0 0 0 1 4(11110000) (11110000) (00000000) (00000000) (00000000) (00000000)(00000000) (11110000)

That is, according to [Table 1], an 8-bit bitmap indicates that SSBs areincluded in SS bursts #0, #1, and #7 and additional informationindicates that 4 SSBs are included in each SS burst. As a result, it maybe estimated that SSBs are transmitted at 4 candidate positions of afront part of each of SS bursts #0, #1, and #7.

Unlike the above-described example, the additional information may alsobe transmitted in a bitmap format so that flexibility of positions atwhich SSBs are transmitted may be obtained.

For example, a method of indicating information related to SS bursttransmission by a bitmap and indicating SSBs transmitted within an SSburst by other bits may be provided.

That is, a total of 64 SSBs are divided into 8 SS bursts (i.e., SSBgroups) and which SS burst is used is indicated to the UE bytransmitting an 8-bit bitmap. If SS bursts are defined as illustrated inFIG. 13, there is an advantage of arranging an SS burst and a boundaryof a slot having a subcarrier spacing of 60 kHz when the SS burst ismultiplexed with the slot having a subcarrier spacing of 60 kHz.Therefore, if the bitmap indicates whether an SS burst is used, the UEmay recognize whether SSBs are transmitted in units of slots for allsubcarrier spacings in the frequency band above 6 GHz.

This example is different from the previously described example in thatthe additional information is indicated in a bitmap format. Then, sincebit map information about 8 SSBs included in each SS burst should betransmitted, 8 bit are needed and the additional information is commonlyapplied to all SS bursts. For example, if the bitmap information aboutSS bursts indicates that SS burst #0 and SS burst #1 are used and theadditional bitmap information about SSBs indicates that first and fifthSSBs are transmitted in the corresponding SS bursts, then the first andfifth SSBs in both SS burst #0 and SS burst #1 are transmitted so thatthe total number of actually transmitted SSBs is 4.

Meanwhile, a few neighbor cells may not be included in a cell list. Theneighbor cells not included in the cell list use a default format for anactually transmitted SSB. By using the default format, the UE maymeasure the neighbor cells not included in the list. In this case, thedefault format may be predefined or may be configured by a network.

Meanwhile, when information about SSBs which are actually transmitted inthe serving cell collides with information about SSBs which are actuallytransmitted in the neighbor cell, the UE may prioritize the informationabout the SSBs which are actually transmitted in the serving cell,thereby acquiring the information about the actually transmitted SSBs.

That is, upon receiving the information about actually transmitted SSBsin a full bitmap format and a grouping format, the UE may prioritize theinformation of the full bitmap format to use the information for SSBreception because there is a high possibility that the information ofthe full bitmap format has high accuracy.

4. System Frame Number (SFN) and Half-Frame Boundary

Low-order N bits of SFN information are transmitted in a PBCH payloadand high-order M bits of the SFN information are transmitted in a PBCHscrambling sequence. Meanwhile one MSB among the high-order M bits ofthe SFN information may be transmitted through variation in atime/frequency position of a PBCH DMRS, an NR-SSS, or an SSB. Inaddition, information about a radio half-frame (5 ms) boundary may betransmitted through variation in the time/frequency position of the PBCHDMRS, the NR-SSS, or the SSB.

Herein, a “high-order bit” or an “MSB” implies a left bit in aninformation bit stream in which a highest-digit number is placed at arightmost position. That is, in the arrangement of the information bitstream in which a highest-digit number is placed at a leftmost position,the “high-order bit” or the “MSB” may be interpreted as having the samemeaning as an LSB, which is a bit giving a units value for determiningwhether a value is even or odd of an integer.

In addition, a “low-order bit” or an “LSB” implies a right bit in aninformation bit stream in which a highest-digit number is placed at arightmost position. That is, in the arrangement of the information bitstream in which a highest-digit number is placed at a leftmost position,the “low-order bit” or the “LSB” may be interpreted as having the samemeaning as the MSB.

Embodiment 1-1

When content that an NR-PBCH included in a specific SSB carries ischanged every 80 ms, the NB-PBCH content includes information which isnot changed within 80 ms. For example, all SFN information included inthe PBCH content is the same within the range of a PBCH TTI (80 ms). Forthis purpose, low-order 7-bit information among 10-bit SFN informationmay be included in the PBCH content and high-order 3-bit informationindicating a frame boundary (10 ms) may be included in the PBCHscrambling sequence.

Embodiment 1-2

When content that an NR-PBCH included in a specific SSB carries ischanged every 80 ms, the NB-PBCH content includes information which isnot changed within 80 ms. For example, all SFN information included inthe PBCH content is the same within the range of a PBCH TTI (80 ms). Tothis end, low-order 7-bit information among 10-bit SFN information isincluded in the PBCH content, low-order 2-bit information amonghigh-order 3-bit information indicating a frame boundary (10 ms) isincluded in the PBCH scrambling sequence, and 1-MSB information istransmitted using other signals or channels which are distinguished froma part associated with PBCH channel coding such as the PBCH content,CRC, the scrambling sequence, etc. For example, the PBCH DMRS may beused as other signals which are distinguished from the part associatedwith PBCH channel coding and may use, as information, a DMRS sequence, aDMRS RE position, DMRS sequence-to-RE mapping change, symbol positionchange within an SSB, and frequency position change of the SSB.

Specifically, when the DMRS sequence is used, a method using adifference in phase between two OFDM symbols in which a DMRS istransmitted, for example, a method of using an orthogonal cover code,may be considered. In addition, when the DMRS sequence is used, a methodof changing an initial value may be considered. Specifically, if aninitial value of one of two m-sequences used for a Gold sequence isfixed and an initial value of the other one of the two m-sequences ischanged using a cell ID and other information, a method of changing aninitial value using information that is desired to be transmitted in them-sequence using the fixed initial value may be introduced.

More specifically, changing two initial values in units of 10 ms withinthe range of 20 ms may be considered by introducing another initialvalue (e.g. [0 1 0 . . . 0]) in addition to an already fixed initialvalue (e.g., [1 0 0 . . . 0]) according to one bit indicating 10-msboundary information. As another method, one m-sequence may use a fixedinitial value and information desired to be transmitted may be added toan initial value of another m-sequence.

When the DMRS RE position is used, a V-shift method of changing afrequency-axis position of the DMRS according to information may beapplied. Specifically, when the DMRS is transmitted at 0 ms and 10 mswithin the range of 20 ms, RE positions are differently arranged. If theDMRS is arranged in every 4 REs, a method of shifting the DMRS REposition in units of 2 REs may be introduced.

In addition, a method of changing PBCH DMRS sequence-to-RE mapping maybe applied. Specifically, in the case of 0 ms, the sequence is mappedstarting from the first RE and, in the case of 10 ms, another sequencemapping method is applied. For example, a method of reversely mappingthe sequence to the first RE, mapping the sequence starting from amiddle RE of the first OFDM symbol, or mapping the sequence startingfrom the first RE of the second OFDM symbol may be applied. In addition,a method of changing an arrangement order of a PSS-PBCH-SSS-PBCH withinan SSB to another arrangement may be considered. For example, while anarrangement order of PBCH-PSS-SSS-PBCH may be basically applied, anotherarrangement method may be applied at 0 ms and 10 ms. In addition, amethod of changing an RE position to which PBCH data is mapped withinthe SSB may be applied.

Embodiment 1-3

1-bit information indicating the half-frame boundary may be transmittedusing other signals or channels distinguished from the part related toPBCH channel coding such as the PBCH content, the CRC, the scramblingsequence, etc. For example, the PBCH DMRS may be used as other signalsdistinguished from the part related to PBCH channel coding as inEmbodiment 1-2 and may use, as information, a DMRS sequence, a DMRS REposition, DMRS sequence-to-RE mapping change, symbol position changewithin an SSB, and frequency position change of the SSB. Particularly,the PBCH DMRS may be applied when time information is changed at a 0-msboundary and a 5-ms boundary within the range of 10 ms.

Additionally, for time change information in units of 5 ms within therange of 20 ms, including half-frame boundary information and 1-MSB SFNinformation, the PBCH DMRS may use, as information, the DMRS sequence,DMRS RE position, DMRS sequence-to-RE mapping change, symbol positionchange in the SSB, and frequency position change of the SSB as proposedin Embodiment 1-2. The PBCH DMRS may be applied when time information ischanged at a boundary of 0, 5, 10, or 15 ms within the range of 20 ms.

Embodiment 1-4

In Embodiment 1-4, a “high-order bit” or an “MSB” implies a left bit inan information bit stream in which a highest-digit number is placed at arightmost position. That is, in the arrangement of the information bitstream in which a highest-digit number is placed at a leftmost position,the “high-order bit” or the “MSB” may be interpreted as having the samemeaning as an LSB, which is a bit giving a units value for determiningwhether a value is even or odd of an integer.

In addition, a “low-order bit” or an “LSB” implies a right bit in aninformation bit stream in which a highest-digit number is placed at arightmost position. That is, in the arrangement of the information bitstream in which a highest-digit number is placed at a leftmost position,the “low-order bit” or the “LSB” may be interpreted as having the samemeaning as the MSB.

When one PBCH consists of a total of N REs, M (<N) REs are allocated forPBCH data transmission. If quadrature phase shift keying (QPSK)modulation is used, the length of a scrambling sequence is 2*M. Togenerate L scrambling sequences having different 2*M lengths, a longsequence of a total length of L*2*M is generated and is divided intosequences in units of 2*M to generate the L Sequences. A pseudo-noise(PN) sequence may be used as a scrambling sequence and a Gold sequenceand an M sequence may also be used. Specifically, a length-31 Goldsequence may be used. As a value for initializing the PN sequence, atleast a cell ID may be used and an SSB index obtained from a PBCH DMRSmay be additionally used. If a slot number or an OFDM symbol are derivedfrom the SSB index, the slot number/OFDM symbol number may be used.Additionally, radio half-frame boundary information may also be used asthe initialization value. In addition, when partial bits among SFNinformation may be acquired as a signal or a channel distinguished froma part related to channel coding, such as content or a scramblingsequence, the SFN information may be used as an initialization value ofthe scrambling sequence.

The length of the scrambling sequence is determined according to thelength of bits transmitted through the scrambling sequence among the SFNinformation. For example, when 3-bit information among the SFNinformation is transmitted through the scrambling sequence, 8 statesshould be expressed. For this purpose, a sequence of a total length of8*2*M is needed. Similarly, when 2-bit information is transmitted, asequence of a total length of 2*2*M is needed.

A bit stream including PBCH content and CRC is encoded using a Polarcode to generate length-512 encoded bits. The length of the encoded bitsis shorter than the length of the scrambling sequence and the bit streamhaving a length equal to the scrambling sequence is generated byrepeating the length-512 encoded bits multiple times. Next, the repeatedencoded bits are multiplied by the scrambling sequence and then aresubjected to QPSK modulation. A modulated symbol is divided intolength-M symbols which are then mapped to PBCH REs.

For example, referring to FIG. 14, when 3-bit information among SFNinformation is transmitted through the scrambling sequence, a length-Mmodulated symbol sequence is transmitted in units of 10 ms in order tochange the scrambling sequence every 10 ms. In this case, modulatedsymbols transmitted in units of 10 ms are different. When a periodicityof an SS burst set is 5 ms, the same modulated symbol sequence istransmitted during two 5-ms transmission periodicities included in therange of 10 ms. If the UE can acquire the radio half-frame (5 ms)boundary information, the UE may combine information of a PBCH which istransmitted twice in the range of 10 ms and perform blind decoding atotal of 8 times to discover 8 scrambling sequences transmitted in unitsof 10 ms in the range of 80 ms. In this case, the UE acquires half-frameboundary 1-bit information (e.g., C0) by decoding a channel other thanthe PBCH. Then, the UE acquires high-order N bits (e.g., S0, S1, and S2)of SFN information by performing PBCH blind decoding and acquires theother (10-N) bits (e.g., S3 to S9) of the SFN information from PBCHcontent, thereby configuring a total of 10 bits of the SFN information.

As another example, when 3-bit information of the SFN information istransmitted through the scrambling sequence and the half-frame boundaryinformation is included in the PBCH content, the same content isincluded in a transmission periodicity of 10 ms. However, sincehalf-frame boundary 1-bit information differs in PBCH content having a5-ms offset, different types of content may be transmitted every 5 ms.That is, two types of content are configured due to the half-frameboundary 1-bit information and a gNB encodes the two types of contentand performs bit repetition, scrambling, and modulation with respect toeach of the two types of content.

If the UE cannot acquire 5-ms boundary information, it is difficult toperform combination of signals transmitted every 5 ms. Instead, the UEequally performs blind decoding of 8 times every 10 ms even in the 5-msoffset. That is, the UE performs blind decoding of at least 8 times toobtain high-order N-bit SFN information (e.g., S0, S1, and S2) andacquires the radio half-frame boundary 1-bit information (e.g., C0) aswell as the other (10-N)-bit SFN information (e.g., S3 to S9) from thePBCH content. In other words, the UE acquires time information in unitsof 5 ms by configuring the obtained bit information.

Similarly, if 2-bit information of the SFN information is transmittedthrough the scrambling sequence, the scrambling sequence is changedevery 20 ms and an equally modulated symbol sequence is transmittedduring four 5-ms transmission periodicities included in the range of 20ms. If the UE can acquire the half fame boundary information and 1-MSBinformation of the SFN information, the UE may combine 4 PBCHs receivedin the range of 20 ms and performs blind decoding of 4 times every 20ms. In this case, although UE reception complexity may increase due toacquisition of the half-frame boundary information and the MSBinformation of the SFN information, complexity of PBCH blind decodingcan be lowered and detection performance can be improved because a PBCHcombination of a maximum of 16 times may be performed. In this case, theUE acquires the half-frame boundary 1-bit information (e.g., C0) and the1-MSB information (e.g., S0) of the SFN information by decoding achannel other than the PBCH.

The UE acquires high-order (N−1)-bit information (e.g., S1 and S2) afterthe 1-MSB of the SFN information by performing PBCH blind decoding andacquires the other (10-N)-bit SFN information (e.g., S3 to S9) from thePBCH content. Then, the radio half-frame boundary information (e.g., C0)and a total of 10 bits (S0 to S9) of SFN information may be configured.Thus, the acquired time information is provided in units of 5 ms. Inthis case, a plurality of SSBs may be transmitted in the range of 5 msand SSB positions in the range of 5 ms may be acquired from the PBCHDMRS and the PBCH content.

Meanwhile, if 2-bit information (e.g., S1 and S2) among the SFNinformation is transmitted through the scrambling sequence and 1-MSBinformation (e.g., S0) among the SFN information and the half-frameboundary 1-bit information (e.g., C0) are transmitted by the PBCHcontent, the PBCH content is changed (e.g., S0 and C0) every 5 ms in therange of 20 ms to generate 4 information bit sets and a channel codingprocess is performed with respect to each information bit set.

As another example, the 10-bit SFN information and the half-frameboundary 1-bit information may be included in the PBCH content. Then,the PBCH content except for high-order 3 bits (e.g., S0, S1, and S2) ofthe SFN information and one bit of the half-frame boundary information(e.g., C0) is not changed during a PBCH TTI (e.g., 80 ms). However, thehigh-order 3 bits (e.g., S0, S1, and S2) of the SFN information and theone bit of the half-frame boundary information (e.g., C0) are in unitsof 5 ms. Hence, 16 PBCH information bit sets may be generated in aduration of the PBCH TTI (e.g., 80 ms).

In addition, a scrambling sequence is applied to information bits exceptfor some bits (e.g., S1 and S2) of SFN information in information bitsincluded in a PBCH payload and to CRC. The scrambling sequence may use aPN sequence such as a Gold sequence. The scrambling sequence may beinitialized by a cell ID.

Meanwhile, when the number of scrambled bits is M, a sequence of alength of M*N is generated and the length-M*N sequence is divided into Nlength-M sequences so as not to overlap elements of the sequences. Eachof the N length-M sequence is used as a scrambling sequence for each ofthe N sequences as described in the following examples according toorder of changing some bits (e.g., S1 and S2) among the SFN information.

(Examples)

When (S2,S1)=(0,0), a sequence stream of 0 to (M−1) is used as thescrambling sequence

When (S2,S1)=(0,1), a sequence stream of M to 2M−1 is used as thescrambling sequence

When (S2,S1)=(1,0), a sequence stream of 2M to 3M−1 is used as thescrambling sequence

When (S2,S1)=(1,1), a sequence stream of 3M to 4M−1 is used as thescrambling sequence

According to the above description, among 16 PBCH information bit setsgenerated in a duration of the PBCH TTI (e.g., 80 ms), the samescrambling sequence is used in 4 PBCH information bit sets transmittedin the range of 20 ms and a scrambling sequence different from thescrambling sequence used for the previous 4 PBCH information bit sets isused in 4 PBCH information bit sets transmitted in the next range of 20ms.

As described above, channel coding is performed with respect to each ofthe 16 PBCH information bit sets which are subject to scrambling using ascrambling sequence and the second scrambling sequence is applied tobits encoded by channel coding. That is, channel coding is performedafter performing scrambling by applying the first scrambling sequence to16 PBCH information bit sets in the same manner as the scheme describedabove. Next, the second scrambling sequence is applied to an acquiredencoded bit. In this case, the second scrambling sequence may use a PNsequence such as a Gold sequence and may be initialized by a cell ID anda 3-bit SSB index transmitted through a PBCH DMRS.

The same scrambling sequence may be used for encoded bits of PBCHcontent transmitted in association with a specific SSB index accordingto a transmission timing.

Meanwhile, a scrambling sequence changed in units of 5 ms may be appliedaccording to the half-frame boundary information. For example, if thenumber of scrambled encoded bits is K, a length-2*K sequence isgenerated and is divided into two sequences each having a length of K soas not to overlap elements of the sequences. The two sequences areapplied according to the half-frame boundary information. According tothe above-described method, when PBCHs transmitted in a duration of 10ms are soft-combined, performance can be improved by randomlydistributing interference.

Meanwhile, if there is no information about a candidate sequence of thesecond scrambling sequence, the UE may perform decoding multiple timesunder the assumption that a scrambling sequence available for acandidate sequence has been transmitted.

The half-frame boundary 1-bit information may be transmitted usingsignals and/or channels different from a part related to channel codingsuch as PBCH content, CRC, a scrambling sequence, etc.

For example, the half-frame boundary 1-bit information may betransmitted using a PBCH DMRS and may be transmitted using a DMRSsequence, a DMRS RE position, and a DMRS sequence-to-RE mapping schemeor order change, a symbol position change of a PSS/SSS/PBCH within anSSB, a frequency position change of the SSB, and polarity inversion ofan SS or a PBCH OFDM symbol. This will be described later in detail.

Before performing PBCH decoding, if the UE acquires the half-frameboundary information, the UE may perform de-scrambling using ascrambling sequence corresponding to the acquired half-frame boundaryinformation.

5. SSB Time Index

A method of indicating an SSB time index will now be described.

Some indexes of SSB time indexes are transmitted in a PBCH DMRS sequenceand the other indexes of the SSB time indexes are transmitted in a PBCHpayload. In this case, the SSB time indexes transmitted in the PBCH DMRSsequence represent N-bit information and the SSB time indexestransmitted in the PBCH payload represent M-bit information. If themaximum number of SSBs in a frequency range is L bits, the L bits arethe sum of M bits and N bits. If a total of H (=2{circumflex over ( )}L)states capable of being transmitted in the range of 5 ms is group A, J(=2{circumflex over ( )}N) states represented by the N bits transmittedin the PBCH DMRS sequence are group B, and I (=2{circumflex over ( )}M)states represented by the M bits transmitted in the PBCH payload aregroup C, then the number H of states of group A may be represented bymultiplication of the number J of states of group B and the number C ofstates of group C. In this case, states of either group B or group C mayrepresent a maximum of P (where P is 1 or 2) within the range of 0.5 ms.Meanwhile, the groups described in the present disclosure have been usedfor convenience of description and various types may be represented asthe groups.

Meanwhile, the number of states transmitted in the PBCH DMRS sequencemay be 4 in the frequency range below 3 GHz, 8 in a frequency rangebetween 3 GHz and 6 GHz, and 8 in the frequency range above 6 GHz. In aband below 6 GHz, subcarrier spacings of 15 kHz and 30 kHz are used. Ifthe subcarrier spacing of 15 kHz is used, a maximum of one state isincluded in the range of 0.5 ms and if the subcarrier spacing of 30 kHzis used, a maximum of two states is included in the range of 0.5 ms. Ina band above 6 GHz, subcarrier spacings of 120 kHz and 240 kHz are used.If the subcarrier spacing of 120 kHz is used, a maximum of one state isincluded in the range of 0.5 ms and if a subcarrier spacing of 240 kHzis used, a maximum of two states is included in the range of 0.5 ms.

FIGS. 15(a) and 15(b) illustrate SSBs included in a range of 0.5 ms whensubcarrier spacings of 15 kHz and 30 kHz are used and subcarrierspacings of 120 kHz and 240 kHz are used, respectively. As illustratedin FIGS. 15, 1, 2, 8, and 16 SSBs are included in a range of 0.5 ms forthe subcarrier spacings of 15 kHz, 30 kHz, 120 kHz, and 240 kHz,respectively.

For the subcarrier spacings of 15 kHz and 30 kHz, indexes of SSBsincluded in 0.5 ms are mapped to indexes transmitted in the PBCH DMRSsequence in one-to-one correspondence. The PBCH payload may include anindication bit for indicating an SSB index. In a band below 6 GHz, theindication bit is not interpreted as a bit for an SSB index and may beinterpreted as information for other purposes. For example, theindication bit may be used for the purpose of coverage expansion and maybe used to transmit the repetition number of signals or resourcesassociated with an SSB.

When the PBCH DMRS sequence is initialized by a cell ID and an SSBindex, for the subcarrier spacings of 15 kHz and 30 kHz, an SSB indextransmitted in the range of 5 ms may be used as an initial value of thesequence. Herein, the SSB index may have the same meaning as the SSB ID(SSBID).

Embodiment 2-1

When a subcarrier spacing is 120 kHz, the number of indexes of SSBsincluded in 0.5 ms is 8. However, in a range of 0.5 ms, the same PBCHDMRS sequence is present and a PBCH payload may vary with an SSB index.It is noted that a PBCH DMRS sequence in a duration of 0.5 ms in which afirst SSB group is transmitted is distinguished from a PBCH DMRSsequence used in a duration of 0.5 ms of a second SSB group transmittedprior to the first SSB group. That is, different sequences are used. Inaddition, to distinguish between SSBs transmitted in different durationsof 0.5 ms, an SSB index for an SSB group is transmitted in the PBCHpayload.

When a subcarrier spacing is 240 kHz, the number of indexes of SSBsincluded in 0.5 ms is 16 and the number of PBCH DMRS sequences in 0.5 msmay be 2. That is, a PBCH DMRS sequence used for 8 SSBs in a front partof 0.5 ms among SSBs may be different from a PBCH DMRS sequence used for8 SSBs in a rear part of 0.5 ms among the SSBs. The PBCH payloadincluded in the SSBs of the front part and the rear part carry SSBindexes.

Thus, when a method of keeping a PBCH DMRS sequence constant during apredetermined time duration is applied, there is an advantage ofacquiring time information having accuracy of about 0.5 ms or 0.25 ms bytransmitting time information based on a PBCH DMRS sequence having lowdetection complexity and high detection performance in the case in whichthe UE attempts to detect a signal of a neighbor cell in order to securetime information of the neighbor cell. This can provide time accuracy ofabout 0.25 ms or 0.5 ms regardless of a frequency range.

Embodiment 2-2

When a subcarrier spacing is 120 kHz, the number of indexes of SSBsincluded in 0.5 ms is 8. However, in a range of 0.5 ms, the same SSB isincluded in the PBCH payload and the PBCH DMRS sequence may vary with anSSB index. It is noted that an SSB index transmitted through the PBCHpayload in a duration of 0.5 ms in which a first SSB group istransmitted is distinguished from an SSB index used in a duration of 0.5ms of a second SSB group transmitted prior to transmission of the firstSSB group. That is, different sequences are used.

When a subcarrier spacing is 240 kHz, the number of indexes of SSBsincluded in 0.5 ms is 16 and the number of SSBs transmitted in the PBCHpayload in the range of 0.5 ms may be 2. That is, SSB indexes includedin the PBCH payload transmitted in 8 SSBs in a duration of 0.5 ms of afront part among SSBs are equal and 8 SSBs in a duration a PBCH DMRSsequence used for 8 SSBs in 0.5 ms of a rear part are different from theSSBs of the front part. In this case, a PBCH DMRS sequence included ineach of the front part and the rear part uses a different sequenceaccording to an SSB index.

When subcarrier spacings are 120 kHz and 240 kHz, SSB indexes areexpressed by a combination of indexes acquired from two paths.Embodiment 2-1 and Embodiment 2-2 described above may be represented by[Equation 1] and [Equation 2], respectively.

SS-PBCH block index=SSBID*P+SSBGID

SSBID=Floor(SS-PBCH block index/P)

SSBGID=Mod(SS-PBCH block index,P)  [Equation 1]

SS-PBCH block index=SSBID*P+SSBGID

SSBID=Mod(SS-PBCH block index,P)

SSBGID=Floor(SS-PBCH block index/P)  [Equation 2]

where P may be expressed by 2{circumflex over ( )}(number of bitstransmitted in PBCH DMRS).

While a specific value (e.g., 4 or 8) has been used for description,this is purely for convenience of description and the present disclosureis not limited to the above-described specific value. For example, theabove-described value may be determined according to the number ofinformation bits transmitted in the PBCH DMRS. If 2-bit information istransmitted in the PBCH DMRS, an SSB group may include 4 SSBs and, evenfor subcarrier spacings of 15 kHz and 30 kHz, the SSB time indextransmission method described for the case of subcarrier spacings of 120kHz and 240 kHz may be applied.

Referring back to FIG. 14, examples of a bit configuration of timeinformation and a transmission path of the time information, describedin “4. System Frame Number (SFN) and Half-Frame Boundary” and “5. SSBtime index”, may be summarized as follows.

-   -   7 bits among 10 bits of an SFN and 3 bits of an SSB group index        are transmitted in PBCH content.    -   2 bits (S2, S1) of 20-ms boundary information are transmitted in        a PBCH scrambling sequence.    -   1 bit (C0) of 5-ms boundary information and 1 bit (S0) of 10-ms        boundary information are transmitted for DMRS RE position shift,        a phase difference in DMRS between OFDM symbols including a        PBCH, a DMRS sequence-to-RE mapping change, or change of a PBCH        DMRS sequence initial value.    -   3 bits (B2, B1, B0) of SSB index indication information are        transmitted in a DMRS sequence.

6. NR-PBCH Content

The UE may detect a cell ID and symbol timing information and thenacquire information, for network access from a PBCH, which includes anSFN, an SSB index, a part of timing information such as a half-frametiming, common control channel related information such as atime/frequency position, bandwidth, bandwidth part information such asan SSB position, and SS burst set information such as SS burst setperiodicity and an actually transmitted SSB index.

Since only a limited time/frequency resource of 576 REs is occupied forthe PBCH, essential information should be included in the PBCH. Ifpossible, an auxiliary signal such as a PBCH DMRS may be used to furtherinclude the essential information or additional information in the PBCH.

(1) SFN

In NR, an SFN is defined to distinguish between intervals of 10 ms.Similarly to an LTE system, the NR system may introduce indexes between0 and 1023 for the SFN and these indexes may be explicitly indicatedusing bits or may be implicitly indicated.

In NR, a PBCH TTI is 80 ms and a minimum periodicity of an SS burst is 5ms. Therefore, a PBCH may be transmitted a maximum of 16 times in unitsof 80 ms and a different scrambling sequence for each transmission maybe applied to a PBCH encoded bit. The UE may detect an interval of 10 mssimilarly to an LTE PBCH decoding operation. In this case, 8 states ofthe SFN may be implicitly indicated by a PBCH scrambling sequence and 7bits for indicating the SFN may be defined by PBCH content.

(2) Timing Information in Radio Frame

An SSB index may be explicitly indicated by bits included in a PBCH DMRSsequence and/or PBCH content according to carrier frequency. Forexample, in the frequency band below 6 GHz, 3 bits of an SSB index aretransmitted only in the PBCH DMRS sequence. In the frequency band above6 GHz, 3 LSBs of the SSB index are expressed as the PBCH DMRS sequenceand 3 MSBs of the SSB index are transmitted by the PBCH content. Thatis, only in the frequency band of 6 GHz to 52.6 GHz, a maximum of 3 bitsfor the SSG index may be defined in the PBCH content.

A half-frame boundary may be transmitted by the PBCH DMRS sequence.Particularly, if a half-frame indication is included in the PBCH DMRSsequence in the frequency band below 3 GHz, this may raise an effectrelative to the case in which the half-frame indication is included inthe PBCH content. That is, since an FDD scheme is mainly used in thefrequency band below 3 GHz, a mismatch degree of time synchronizationbetween a subframe and a slot may be big. Accordingly, in order toachieve more accurate time synchronization, it is favorable to transmitthe half-frame indication through the PBCH DMRS which has betterdecoding performance than the PBCH content.

However, since a TDD scheme is mainly used in a band above 3 GHz, amismatch degree of time synchronization between a subframe and a slotwill not be big. Therefore, there may be few disadvantages even if thehalf-frame indication is transmitted through the PBCH content.

Meanwhile, the half-frame indication may also be transmitted throughboth the PBCH DMRS and the PBCH content.

(4) Information for Identifying Absence of RMSI Corresponding to PBCH

In NR, an SSB may be used for operation measurement as well as provisionof information for network access. Particularly, for a broadband CCoperation, multiple SSBs may be transmitted for measurement.

However, it may be unnecessary to transmit RMSI through all frequencypositions in which the SSBs are transmitted. That is, the RMSI may betransmitted through a specific frequency position for the purpose ofefficiency of resource use. In this case, UEs performing an initialaccess procedure cannot recognize whether the RMSI is provided at adetected frequency position. To solve this problem, a bit field foridentifying that the RMSI corresponding to a PBCH of a detectedfrequency region is absent needs to be defined. Meanwhile, a method ofidentifying that the RMSI corresponding to the PBCH is absent withoutproviding the bit field also needs to be considered.

To this end, an SSB having no RMSI may be transmitted at a frequencyposition which is not defined as frequency raster. In this case, sincethe UEs performing the initial access procedure cannot detect the SSB,the above-described problem can be solved.

(5) SS Burst Set Periodicity and Actually Transmitted SSB

For the purpose of measurement, information about SS burst setperiodicity and an actually transmitted SSB may be indicated. Therefore,this information is desirably included in system information for cellmeasurement and inter/intra-cell measurement. In other words, it is notnecessary to define the above information in the PBCH content.

(8) Payload Size

In consideration of the decoding performance of a PBCH, it may beassumed that a payload size of a maximum of 64 bits is provided asillustrated in [Table 2].

TABLE 2 Bit size Below Above Details 6 GHz 6 GHz System Frame Number(MSB)  7  7 SS/PBCH block time index (MSB)  0  3 Reference numerology [1]  [1] Bandwidth for DL common channel,  [3]  [2] and SS blockposition # of OFDM symbols in a Slot  [1]  0 CORESET About [10] About[10] (Frequency resource-bandwidth, location) (Time resource-startingOFDM symbol, duration) (UE Monitoring periodicity, offset, duration)Reserved Bit [20] [20] CRS 16 + a 16 + a Total 64 64

7. NR-PBCH Scrambling

The type of an NR-PBCH scrambling sequence and the initialization of thesequence will now be described. Although use of a PN sequence may beconsidered in NR, it is desirable to reuse a Gold sequence as theNR-PBCH scrambling sequence unless a serious problem arises due to useof a length-31 Gold sequence defined in an LTE system as the NR-PBCHsequence.

In addition, the scrambling sequence may be initialized by at least acell ID and 3 bits of an SSB index indicated by a PBCH-DMRS may be usedfor initialization of the scrambling sequence. If a half-frameindication is indicated by the PBCH-DMRS or other signals, thehalf-frame indication may also be used as a seed value for initializingthe scrambling sequence.

8. PBCH Coding Chain Configuration and PBCH DMRS Transmission Scheme

An embodiment of a PBCH coding chain configuration and a PBCH DMRStransmission scheme will now be described with reference to FIG. 16.

First, an MIB configuration may differ according to control resource set(CORESET) information per SSB and an SSB group index. Therefore,encoding is performed with respect to an MIB per SSB and the size ofencoded bits is 3456 bits. Since polar code output bits are 512 bits,the polar code output bits may be repeated 6.75 times (512*6+384).

A length-3456 scrambling sequence is multiplied by the repeated bits andthe scrambling sequence is initialized by a cell ID and an SSB indextransmitted in a DMRS. The 3456-bit scrambling sequence is divided into4 groups each having 864 bits and QPSK modulation is performed withrespect to each group so that 4 length-432 modulated symbol sets areconfigured.

A new modulated symbol set is transmitted every 20 ms and the samemodulated symbol set may be transmitted a maximum of 4 times within 20ms. In a duration in which the same modulated symbol set is repeatedlytransmitted, a frequency-axis position of a PBCH DMRS is shiftedaccording to a cell ID. That is, a DMRS position is shifted by [Equation3] every 0/5/10/15 ms.

vshift=(vshift_cell+vshift_frame)mod 4,vshift_cell=Cell-ID mod3,vshift_frame=0,1,2,3  [Equation 3]

A PBCH DMRS sequence uses a length-31 Gold sequence. An initial value ofa first m-sequence is fixed as one value and an initial value of asecond m-sequence is determined based on the SSB index and the cell IDas indicated by [Equation 4].

cinit=210*(SSBID+1)*(2*CellID+1)+CellID  [Equation 4]

If the content of SSBs is the same, channel coding and bit repetitionmay be performed only with respect to one SSB. In addition, if adifferent scrambling sequence value is applied to each SSB, a process ofgenerating and multiplying the scrambling sequence and a process ofsegmenting and modulating bits are performed with respect to each SSB.

Hereinafter, operations of a gNB and a UE according to a method oftransmitting radio half-frame information and one MSB of an SFN will bedescribed. C0 and S0 described hereinbelow correspond to a half-frameboundary bit and a frame boundary indication bit of FIG. 14,respectively.

(1) C0 and S0 are Transmitted in CRC:

C0 and S0 are information changed every 0, 5, 10, or 15 ms. A total of 4CRCs is generated and encoding of 4 times is performed. Then, eachencoded bit is repeatedly arranged under the assumption that the encodedbit is transmitted a total of 4 times every 20 ms and the encoded bit ismultiplied by the scrambling sequence.

During reception by the UE, blind decoding should further be performedto combine information received every 0, 5, 10, or 15 ms. Although thereis no additional complexity if only PBCHs received every 20 ms areblind-decoded, it is difficult to guarantee maximum performance becausesignals transmitted every 5 ms cannot be combined.

(2) C0 and S0 are Transmitted in PBCH Scrambling:

Encoding is performed using one type of information bit and using CRC.Then, an encoded bit is repeatedly arranged under the assumption thatthe encoded bit is transmitted every 5 ms, i.e., a total of 16 times,and the encoded bit is multiplied by the scrambling sequence. Thismethod is problematic in that the number of times performing blinddecoding increases to 16.

(3) C0 and S0 are Transmitted in DMRS Sequence:

5 bits are transmitted in a length-144 sequence and encoding isperformed using one type of information and using CRC. There are twoscrambling schemes.

1) An encoded bit repeatedly arranged, under the assumption that theencoded bit is transmitted every 5 ms, i.e., the encoded bit istransmitted a total of 16 times, and the encoded bit is multiplied bythe scrambling sequence. In this case, since the scrambling sequence ischanged every 5 ms, inter-cell interference (ICI) randomization of aPBCH may occur. Since the UE acquires information of C0 and S0 from theDMRS sequence, the UE may acquire scrambling sequence informationchanged every 0, 5, 10, or 15 ms. The number of times of blind decodingdoes not increase during PBCH decoding. The above method combines asignal transmitted every 5 ms and thus maximum performance can beexpected.

2) An encoded bit repeatedly arranged, under the assumption that theencoded bit is transmitted every 20 ms, i.e., the encoded bit istransmitted a total of 4 times, and the encoded bit is multiplied by thescrambling sequence. Then, ICI randomization may be reduced. Performanceimprovement can be expected without increasing the number of times ofblind decoding of the UE and acquisition time can be improved.

However, since a plurality of bits should be included in a DMRS sequencewhen C0 and S0 are transmitted in the DMRS sequence, detectionperformance may be reduced and the number of times of blind decoding mayincrease. To overcome these problems, combining should be performedmultiple times.

(4) C0 and S0 are Transmitted Through DMRS Position:

A basic principle of this case is identical to transmission of C0 and S0in the DMRS sequence. However, to transmit C0 and S0 through the DMRSposition, the position is determined based on a cell ID and a frequencyposition is shifted by 0, 5, 10, or 15 ms. Even a neighbor cell mayshift the position in the same manner. Particularly, if power boostingis performed with respect to a DMRS, performance can be furtherimproved.

9. NR-PBCH DM-RS Design

An NR-PBCH DMRS should be scrambled by 1008 cell IDs and a 3-bit SSBindex. This is because detection performance of 3 bits exhibits the mostappropriate result for the number of hypotheses of the DMRS sequencewhen detection performance is compared according to the number ofhypotheses for the DMRS sequence. However, since detection performanceof 4 or 5 bits has almost no detection performance loss, the number ofhypotheses of 4 or 5 bits may also be used.

Meanwhile, since an SSB time index and a 5-ms boundary should beindicated through the DMRS sequence, the DMRS sequence should bedesigned to have a total of 16 hypotheses.

In other words, the DMRS sequence should be capable of representing atleast a cell ID, an SSB index in an SS burst set, and a half-frameboundary (or half-frame indication) and may be initialized by the cellID, the SSB index in the SS burst set, and the half-frame boundary (orhalf-frame indication). A detailed initialization equation is indicatedby [Equation 5].

c _(init)=(N _(ID) ^(SS/PBCH block)+1+8·HF)·(2·N _(ID) ^(cell)+1)·2¹⁰ +N_(ID) ^(cell)  [Equation 5]

where N_(ID) ^(SS/PBCH block) is an SSB index within an SSB group,N_(ID) ^(Cell) is a cell ID, and HF is a half-frame indication indexhaving a value of {0, 1}.

The NR-PBCH DMRS sequence may be generated based on a length-31 Goldsequence similarly to an LTE DMRS sequence or based on a length-7 or 8Gold sequence.

Meanwhile, since detection performance when the length-31 Gold sequenceis similar to detection performance when the length-7 or 8 Gold sequenceis used, the present disclosure proposes using the length-31 Goldsequence as in the LTE DMRS. In the frequency range above 6 GHz, a Goldsequence having a longer length than the length-31 Gold sequence may beconsidered.

A DMRS sequence r_(N) _(ID) _(SS/PBCH block) (m) which is modulatedusing QPSK may be defined by [Equation 6].

$\begin{matrix}{{{r_{N_{ID}^{{SS}/{PBCHblock}}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},\mspace{20mu} {m = 0},1,\ldots \mspace{14mu},143} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

As a modulation type for generating the DMRS sequence, BPSK and QPSK maybe considered. Although detection performance of BPSK is similar to thatof QPSK, since correlation performance of QPSK is better than that ofBPSK, QPSK is more proper as the modulation type for generating the DMRSsequence.

Now, a method of configuring the PBCH DMRS sequence will be described inmore detail. The PBCH DMRS sequence uses a Gold sequence. Twom-sequences are configured by polynomials having the same length. Whenthe length of a sequence is short, one m-sequence may be replaced with apolynomial of a short length.

Embodiment 3-1

Two m-sequences constituting the Gold sequence are configured with thesame length. An initial value of one of the m-sequences may use a fixedvalue and an initial value of the other one of the m-sequences may beinitialized by a cell ID and a time indication.

For example, the Gold sequence may use a length-31 Gold sequence used inLTE. A CRS of legacy LTE uses the length-31 Gold sequence and isinitialized by 504 cell IDs, and 140 time indications based on 7 OFDMsymbols and 20 slots, thereby generating different sequences.

Since subcarrier spacings of 15 kHz and 30 kHz are used in a band below6 GHz, the maximum number of SSBs included in a range of 5 ms may be 8and the maximum number of SSBs included in a range of 20 ms may be 32.That is, if information about a 5-ms boundary in a range of 20 ms isacquired through a PBCH DMRS sequence, the same operation as anoperation of searching for 32 SSBs is performed. Although the number ofcell IDs of NR is increased to 1008 which is twice that in LTE, sincethe number of SSBs which should be distinguished is less than 70(=140/2), the above-described sequence may be used.

Meanwhile, although the maximum number of SSBs is 64 in a range of 5 msin a band above 6 GHz, the maximum number of SSBs transmitted by a PBCHDMRS is 8 which is equal to the maximum number of SSB indexes in a bandbelow 6 GHz. Accordingly, a length-31 Gold sequence may be used even ina band above 6 GHz so that a sequence may be generated according thecell ID and the time indication.

As another method, Gold sequences of different lengths may be appliedaccording to a frequency range. In a band above 6 GHz, a subcarrierspacing of 120 kHz and a subcarrier spacing of 240 kHz may be used.Then, the number of slots included in 10 ms is increased to 8 times(i.e., 80 slots) and 16 times (i.e., 160 slots) as compared with thecase in which a subcarrier spacing of 15 kHz is used. Particularly, if asequence of a data DMRS is initialized using a 16-bit C-RNTI and a slotindex, a polynomial having a longer length than a legacy length of 31may be needed. According to such requirement, if a length-N (>31) Goldsequence is introduced, this sequence may be used for a PBCH DMRS andPBCH scrambling. Then, Gold sequences having different lengths may beapplied according to a frequency range. A length-31 Gold sequence may beused in a band below 6 GHz and a length-N(>31) Gold sequence may be usedin a band above 6 GHz. In this case, an initial value may be appliedsimilarly to the above-described scheme.

Embodiment 3-2

Two m-sequences constituting the Gold sequence are configured with thesame length. One of the m-sequences may be initialized by a timeindication and an initial value of the other one of the m-sequences maybe initialized by a cell ID or by the cell ID and another timeindication. For example, the Gold sequence may use a length-31 Goldsequence used in LTE. An m-sequence to which a fixed initial value isconventionally applied is initialized by the time indication and anotherm-sequence is initialized by the cell ID.

As another method, if a radio half-frame boundary (5 ms) and one MSB ofan SFN (10-ms boundary) among time indications are transmitted togetherwith an SSB index in a PBCH DMRS, the radio half-frame boundary (5 ms)and one MSB of the SFN (10-ms boundary) may be indicated in the firstm-sequence and the SSB index may be indicated in the second m-sequence.

As proposed in Embodiment 3-1 described above, even when Gold sequenceshaving different lengths according to a frequency range are introduced,the above-described sequence initialization method may be applied.

Embodiment 3-3

A Gold sequence is configured by m-sequences having polynomials ofdifferent lengths. An m-sequence having a long polynomial is used forinformation requiring many indications and an m-sequence having arelatively short polynomial is used for information requiring fewindications.

A sequence of a PBCH DMRS is generated according to a cell ID and timeinformation such as an SSB indication. Two polynomials of differentlengths may be used to represent 1008 cell IDs and P pieces of timeinformation (e.g., a 3-bit SSB indicator). For example, a length-31polynomial may be used to distinguish between cell IDs and a length-7polynomial may be used to distinguish between time information. Each ofthe two m-sequences may be initialized by the cell ID and the timeinformation. Meanwhile, in the above-described example, the length-31polynomial may be a part of m-sequences constituting the Gold sequencein LTE and the length-7 polynomial may be one of two m-sequences definedto constitute an NR-PSS or NR-SSS sequence.

Embodiment 3-4

A sequence is generated from an m-sequence having a polynomial of ashort length and a sequence is generated from a Gold sequence consistingof m-sequences having a polynomial of a long length. Then, the twosequences are multiplied element-wise.

Hereinafter, a method of setting an initial value of a sequence used asa PBCH DMRS sequence will be described. The PBCH DMRS sequence isinitialized by a cell ID and a time indication. If a bit stream used forinitialization is expressed as c(i)*2{circumflex over ( )}i, i=0, . . ., 30, c(0) to c(9) are determined by the cell ID and c(10) to c(30) aredetermined by the cell ID and the time indication. In particular, bitscorresponding to c(10) to c(30) carry a part of information of the timeindication and an initialization method may vary according to anattribute of the information of the time indication.

Embodiment 4-1

During initialization according to the cell ID and the SSB index, c(0)to c(9) are determined by the cell ID and c(10) to c(30) are determinedby the cell ID and the SSB index as described above. In [Equation 7]below, NID denotes the cell ID and SSBID denotes the SSB index.

2{circumflex over ( )}10*(SSBID*(2*NID+1))+NID+1

2{circumflex over ( )}10*((SSBID+1)*(2*NID+1))+NID+1

2{circumflex over ( )}10*((SSBID+1)*(2*NID+1))+NID  [Equation 7]

Embodiment 4-2

If the time indication is added in the initialization scheme describedin Embodiment 4-1, an initial value is set in the form of increasing anSSB. When the number of SSB indexes transmitted in the PBCH DMRSsequence in a range of 5 ms is P, if it is desired to search for a radiohalf-frame boundary from the DMRS sequence, this may be expressed as aneffect of doubling the number of SSB indexes. In addition, if it isdesired to search for a boundary of 10 ms as well as the half-frameboundary, this may be expressed as an effect of increasing the number ofSSB indexes four times. An equation for Embodiment 4-2 described hereinis indicated by [Equation 8].

2{circumflex over ( )}10*((SSBID+P*(i))*(2*NID+1))+NID+1

2{circumflex over ( )}10*((SSBID+1+P*(i))*(2*NID+1))+NID+1

2{circumflex over ( )}10*((SSBID+1+P*(i))*(2*NID+1))+NID  [Equation 8]

When boundaries of 0, 5, 10, and 15 ms are expressed, then i=0, 1, 2, 3and when only a half-frame boundary is expressed, then i=0, 1.

Embodiment 4-3

If the time indication is added in the initialization scheme describedin Embodiment 4-1, the time indication may be indicated by beingdistinguished from the SSB index. For example, c(0) to c(9) may bedetermined by the cell ID, c(10) to c(13) may be determined by the SSBindex, and c(14) to c(30) may be determined by the added time indicationsuch as a half-frame boundary or SFN information. An equation forEmbodiment 4-3 described herein is indicated by [Equation 9].

2{circumflex over ( )}13*(i)+2{circumflex over ( )}10*((SSBID+1))+NID

2{circumflex over ( )}13*(i+1)+2{circumflex over ( )}10*((SSBID+1))+NID

2{circumflex over ( )}13*(i)+2{circumflex over ( )}10*((SSBID+1))+NID+1

2{circumflex over ( )}13*(i+1)+2{circumflex over( )}10*((SSBID+1))+NID+1  [Equation 9]

Embodiment 4-4

According to a frequency range, the maximum number L of SSBs isdetermined. If the number of SSB indexes transmitted in the PBCH DMRSsequence is P and L is less than or equal to P, all SSB indexes aretransmitted in the DMRS sequence and the SSB indexes are identical toindexes acquired from the DMRS sequence. Meanwhile, if L is greater thanP, the SSB indexes are configured by a combination of indexestransmitted in the DMRS sequence and indexes transmitted in PBCHcontent.

When an index used in the DMRS sequence is an SSBID and an indexincluded in the PBCH content is an SSBGID, the following three cases maybe considered.

(1) Case 0: L<=P

SS-PBCH block index=SSBID

(2) Case 1: L>P

SS-PBCH block index=SSBID*P+SSBGID

SSBID=Floor (SS-PBCH block index/P)

SSBGID=Mod(SS-PBCH block index, P)

(3) Case 2: L>P

SS-PBCH block index=SSBID*P+SSBGID

SSBID=Mod(SS-PBCH block index, P)

SSBGID=Floor (SS-PBCH block index/P)

Meanwhile, a pseudo-random sequence for generating an NR-PBCH DMRSsequence is defined as a length-31 Gold sequence and a length-M_(PN)sequence c(n) is defined by [Equation 10].

c(n)=(x ₁(n+N _(C))+x ₂(n+N _(C)))mod 2

x ₁(n+31)=(x ₁(n+3)+x ₁(n))mod 2

x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₂(n))mod 2  [Equation 10]

where n=0, 1, . . . , N_(PN)−1, N_(C)=1600, a first m-sequence has aninitial value of x₁(0)=1, x₁(n)=0, n=1, 2, . . . , 30, and an initialvalue of a second m-sequence is defined by c_(init)=Σ_(i=0)³⁰x₂(i)·2^(i). In this case,

${{x_{2}(i)} = {\left\lfloor \frac{C_{init}}{2^{i}} \right\rfloor {mod}\ 2}},{i = 0},1,\ldots \mspace{14mu},30.$

10. NR-PBCH DMRS Pattern Design

In relation to a frequency position of a DMRS, two DMRS RE mappingmethods may be considered. A fixed RE mapping method serves to fix an RSmapping region in the frequency domain and a variable RE mapping methodserves to shift an RS position according to a cell ID using a Vshiftmethod. The variable RE mapping method is advantageous in thatadditional performance gain can be obtained by randomizing interferenceso that it is desirable to use the variable RE mapping method.

The variable RE mapping method will now be described in detail. Acomplex modulation symbol a_(k,l) included in a half-frame may bedetermined by [Equation 11].

$\begin{matrix}{{a_{k,l} = {r_{N_{ID}^{{SS}/{PBCHblock}}}\left( {{72 \cdot l^{\prime}} + m^{\prime}} \right)}}{k = {{{4m^{\prime}} + {v_{shift}\mspace{14mu} {if}\mspace{14mu} l}} \in \left\{ {1,3} \right\}}}{l = \left\{ {{{\begin{matrix}1 & {l^{\prime} = 0} \\3 & {l^{\prime} = 1}\end{matrix}m^{\prime}} = 0},1,\ldots \mspace{14mu},{{71v_{shift}} = {N_{ID}^{cell}{mod}\; 3}}} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 11} \right\rbrack\end{matrix}$

where k and l represent a subcarrier and an OFDM symbol index locatedwithin an SSB and r_(N) _(ID) _(SS/PBCH block) (m) represents a DMRSsequence. Meanwhile, Vshift may be determined by V_(shift)=N_(ID)^(cell) mode 4.

In addition, RS power boosting may be considered for performanceimprovement. If both RS power boosting and Vshift are used, interferencefrom total radiated power (TRP) may be reduced. In consideration ofdetection performance gain of RS power boosting, the ratio of PDSCHenergy per resource element (EPRE) to RS EPRE is desirably −1.25 dB.

Hereinafter, a method of mapping a PBCH DMRS sequence to an RE will bedescribed.

Embodiment 5-1

The length of a sequence for a DMRS is determined by the number of REsused for a PBCH DMRS and a modulation order.

If M REs are used for the PBCH DMRS and a sequence is modulated by BPSK,a length-M sequence is generated. BPSK modulation is performed insequence order and a modulated symbol is mapped to DMRS REs. Forexample, when a total of 144 PBCH DMRS REs is present in two OFDMsymbols, a length-144 sequence is generated using one initial value,BPSK modulation is performed, and then RE mapping is performed.

Meanwhile, when M REs are used for the PBCH DMRS and QPSK modulation isperformed, a length-2*M sequence is generated. If a sequence stream iss(0), . . . , s(2*M−1), QPSK modulation is performed by combiningsequences of even indexes and odd indexes. For example, when a total of144 PBCH DMRS REs is present in two OFDM symbols, a length-288 sequenceis generated using one initial value, QPSK modulation is performed, andthen a generated length-144 modulated sequence is mapped to the DMRSREs.

If N REs are used for the PBCH DMRS in one OFDM symbol and a sequence ismodulated by BPSK, a length-N sequence is generated. BPSK modulation isperformed in sequence order and a modulated symbol is mapped to DMRSREs. For example, when a total of 72 PBCH DMRS REs is present in oneOFDM symbol, a length-72 sequence is generated using one initial value,BPSK modulation is performed, and then RE mapping is performed. If oneor more OFDM symbols are used for PBCH transmission, initialization isperformed with respect to each OFDM symbol to generate differentsequences or a sequence generated in a previous symbol may be equallymapped.

When N REs are used for the PBCH DMRS in one OFDM symbol and a sequenceis modulated by QPSK, a length-2*N sequence is generated. If a sequencestream is s(0), . . . , s(2*M−1), QPSK modulation is performed bycombining sequences of even indexes and odd indexes. For example, when atotal of 72 PBCH DMRS REs is present in one OFDM symbol, a length-144sequence is generated using one initial value, QPSK modulation isperformed, and then RE mapping is performed. If one or more OFDM symbolsare used for PBCH transmission, initialization is performed with respectto each OFDM symbol to generate different sequences or a sequencegenerated in a previous symbol may be equally mapped.

Embodiment 5-2

When the same sequence is mapped to different symbols, cyclic shift maybe applied. For example, when two OFDM symbols are used, if a modulatedsequence stream of a first OFDM symbol is sequentially mapped to REs, amodulated sequence stream of a second OFDM symbol is cyclic-shifted byan offset corresponding to ½ of a modulated sequence stream N and thenare mapped to REs. When an NR-PBCH uses 24 RBs, an NR-SSS uses 12 RBs,and the NR-SSS is desired to equalize middle frequency REs with theNR-PBCH, the NR-SSS is arranged from the 7th RB to the 18th RB. Channelestimation from the NR-SSS may be performed. Upon detecting an SSB indexfrom the NR-PBCH DMRS, the UE may attempt to perform coherent detectionusing the estimated channel. If the cyclic shift method is applied toeasily perform estimation, an effect of transmitting a sequence streamof the PBCH DMRS in two OFDM symbols in a region of middle 12 RBs inwhich the NR-SSS is transmitted may be obtained.

Embodiment 5-3

When other time indications in addition to the SSB indication aretransmitted, a cyclic shift value may be determined according to thetime indications.

When the same sequence is mapped to OFDM symbols, the same cyclic shiftmay be applied to each OFDM symbol or a different cyclic shift may beapplied to each OFDM symbol. If sequences corresponding to the totalnumber of DMRS REs included in an OFDM symbol used as a PBCH aregenerated, cyclic shifts are applied to all sequences and then aremapped to DMRS REs. As another example of cyclic shifts, reverse mappingmay be considered. For example, if a modulated sequence stream is s(0),. . . , s(M−1), reverse mapping may be s(M−1), . . . , s(0).

Hereinafter, a frequency position of a PBCH DMRS RE will be described.

A frequency position of an RE used for the PBCH DMRS may be changed by aspecific parameter.

Embodiment 6-1

If a DMRS is arranged in every N (e.g., N=4) REs, a maximum shiftedrange of an RE position of the frequency axis may be set to N. Forexample, the maximum shifted range may be N*m+v_shift (where, m=0, . . ., 12×NRB_PBCH-1, v_shift=0, . . . , N−1).

Embodiment 6-2

A shifted offset of the frequency axis may be determined by at least acell ID. The shifted offset may be determined using a cell ID obtainedfrom a PSS and an SSS. A cell ID of an NR system may be configured by acombination of Cell_ID(1) obtained from the PSS and Cell_ID(2) obtainedfrom the SSS and the cell ID may be represented byCell_ID(2)*3+Cell_ID(1). The shifted offset may be determined using cellID information obtained in this way or a part of the cell IDinformation. An example of calculating the offset is indicated by[Equation 12].

v_shift=Cell-ID mod N (where N is a frequency interval of a DMRS, forexample, N is set to 4)

v_shift=Cell-ID mod 3 (interference randomization effect between 3contiguous cells. A DMRS frequency interval may be wider than 3. Forexample, N=4)

v_shift=Cell_ID(1)(Cell_ID(1) obtained from the PSS is used as a shiftedoffset)  [Equation 12]

Embodiment 6-3

A shifted offset of the frequency axis may be determined by a part oftime information. For example, the shifted offset may be determined by aradio half-frame boundary (5 ms) or 1-MSB information of an SFN (10 msboundary). An example of calculating the offset may be indicated by[Equation 13].

v_shift=0,1,2,3 (The position of a DMRS is shifted in every 0/5/10/15ms. When a frequency interval of a DMRS is 4, there are 4 shiftedopportunities)

v_shift=0,1 (The position of the DMRS is shifted according to a 0/5-msboundary or a 0/10-ms boundary)

v_shift=0,2 (The position of the DMRS is shifted according to a 0/5 msboundary or a 0/10 ms boundary. When a frequency interval of the DMRS is4, the position of the DMRS is shifted by 2, which is a maximuminterval)  [Equation 13]

Embodiment 6-4

A shifted offset of the frequency axis may be determined by a cell IDand a partial value of time information. For example, the offset may beconfigured by a combination of Embodiment 6-2 and Embodiment 6-3. Theoffset is configured by vshift_cell, which is a shift according to acell ID, and vshift_frame, which is a shift according to the timeinformation. The offset may be represented by a modulo of a DMRS REinterval N. An embodiment for calculating the offset may be indicated by[Equation 14].

vshift=(vshift_cell+vshift_frame)mod N  [Equation 14]

FIG. 17 is a diagram illustrating DMRS mapping in an SSB.

Hereinafter, the ratio of power between a PBCH DMRS RE and a data REwill be described. An RE used for PBCH DMRS transmission may betransmitted at higher power than an RE used for data transmission in anOFDM symbol in which a PBCH DMRS is included.

Embodiment 7-1

The ratio of energy per data RE to energy per DMRS RE uses a fixed valuein each frequency band. In this case, the fixed value may be used in allfrequency bands or a specific power ratio may be applied to a specificfrequency band. That is, a different power ratio may be used in eachfrequency band. For example, high power may be used in a band below 6GHz in which ICI dominantly functions and the same power may be used ina band above 6 GHz in an environment in which noise is limited.

In the present disclosure, while the ratio of power has been expressedas “the ratio of energy per data RE to energy per DMRS RE” forconvenience of description, various other expressions may be used asfollows.

-   -   Ratio of power per DMRS RE to power per data RE    -   Ratio of energy per DMRS RE to energy per data RE    -   Ratio of power per data RE to power per DMRS RE    -   Ratio of energy per data RE to energy per DMRS RE

Embodiment 7-2

Power of an RE used for a DMRS may be set to a value lower than power ofRE used for data by 3 dB. For example, if PBCH decoding performance when3 REs among 12 REs are used for the DMRS and 9 REs are used for the datais similar to PBCH decoding performance when 4 REs and 8 REs are usedfor the DMRS and the data, respectively, and if it is desired to obtaina similar effect when 3 REs are used for the DMRS and when 4 REs areused for the DMRS, power of the DMRS of 3 REs may be improved to 1.3334times per RE and power of neighbor data REs may be adjusted to 0.8889times, thereby increasing power of the DMRS while maintaining totalpower of OFDM symbols. In this case, a power boosting level is about1.76 dB (=10 log(1.3334/0.8889)).

As another example, when 3 REs and 9 REs are used for the DMRS and thedata, respectively, and detection performance in similar as comparedwith the case in which 4 REs and 8 REs are used for the DMRS and thedata, respectively, the power boosting level is about 3 dB (4.15RE DMRSis about 2 dB)

Embodiment 7-3

If the NR system performs a non-stand-alone (NSA) operation inassociation with the LTE system, the gNB may indicate the ratio ofenergy per data RE to energy per DMRS RE.

Embodiment 7-4

The gNB may indicate, to the UE, the ratio of energy per PBCH data RE toenergy per DMRS RE used in an NR system. For example, the UE maydemodulate PBCH data in an initial access procedure under the assumptionthat the ratio of energy per PBCH data RE to energy per DMRS RE is thesame. Next, the gNB may indicate the ratio of energy actually used fortransmission to the UE. Particularly, the gNB may indicate an energyratio for a target cell among configurations for handover.

As another example, the gNB may indicate the energy ratio together withsystem information indicating transmission power of a PBCH DMRS for aserving cell. At least one of indicated energy ratio values indicates 0dB. If transmission power of the DMRS increases or decreases, the gNBmay include an increased or decreased value in an indicated energy ratiovalue.

11. Time Index Indication Method

Referring to FIG. 18, time information includes an SFN, a half-frameboundary, and an SSB time index. The time information may be representedby 10 bits for the SFN, 1 bit for a half-frame boundary, and 6 bits forthe SSB time index. In this case, a part of the 10 bits for the SFN maybe included in PBCH content. In addition, an NR-PBCH DMRS may include 3bits among the 6 bits for the SSB index.

Embodiments of the time index indication method represented in FIG. 18may be as follows.

-   -   Method 1: S2 S1 (PBCH scrambling)+S0 C0 (PBCH contents)    -   Method 2: S2 S1 S0 (PBCH scrambling)+C0 (PBCH contents)    -   Method 3: S2 S1 (PBCH scrambling)+S0 C0 (PBCH DMRS)    -   Method 4: S2 S1 S0 (PBCH scrambling)+C0 (PBCH DMRS)

If a half-frame indication is transmitted through the NR-PBCH DMRS,additional performance improvement can be obtained by combining PBCHdata every 5 ms. For this reason, 1 bit for the half-frame indicationmay be transmitted through the NR-PBCH DMRS as in Method 3 and Method 4.

When comparing Method 3 with Method 4, while Method 3 may reduce thenumber of times of blind decoding, there may be loss of PBCH DMRSperformance. If the PBCH DMRS can transmit 5 bits including S0, C0, B0,B1, and B2 with excellent performance, Method 3 may be proper for thetime indication method. However, if the PBCH DMRS cannot transmit the 5bits with excellent performance, Method 4 may be proper for the timeindication method.

When the above description is considered, 7 MSBs of the SFN may beincluded in the PBCH content and 2 or 3 LSBs may be transmitted througha PBCH scrambling sequence. In addition, 3 LSBs of the SSB index may beincluded in the PBCH DMRS and 3 MSBs of the SSB index may be included inthe PBCH content.

Additionally, a method of acquiring an SSB time index of a neighbor cellmay be considered. Since decoding through the DMRS sequence exhibitsbetter performance than decoding through the PBCH content, 3 bits of theSSB index may be transmitted by changing the DMRS sequence within eachduration of 5 ms.

Meanwhile in the frequency range below 6 GHz, the SSB time index may betransmitted using only an NR-PBCH DMRS of a neighbor cell, whereas, inthe frequency range above 6 GHz, 64 SSB indexes are divided through thePBCH-DMRS and the PBCH content. Therefore, the UE needs to decode a PBCHof the neighbor cell.

However, decoding of both the PBCH-DMRS and the PBCH content may causeadditional complexity of NR-PBCH decoding and reduce decodingperformance of the PBCH relative to decoding of the PBCH-DMRS alone.Hence, it may be difficult to decode the PBCH in order to receive an SSBof the neighbor cell.

Accordingly, instead of decoding the PBCH of the neighbor cell,providing a configuration related to the SSB index of the neighbor cellto the UE by the serving cell may be considered. For example, theserving cell provides a configuration regarding 3 MSBs of the SSB indexof a target neighbor cell to the UE and the UE detects 3 LSBs throughthe PBCH-DMRS of the target neighbor cell. Then, the UE may acquire theSSB index of the target neighbor cell by combining the 3 MSBs and the 3LSBs.

The above description will now be given supplementarily. The UE acquires3 MSBs of an SSB index of an SSB transmitted by the serving cell throughPBCH content of the SSB received from the serving cell and detects 3LSBs of the SSB index of the SSB transmitted by the serving cell througha PBCH-DMRS. Then, the UE receives another SSB from a neighbor cell anddetects 3 LSBs of an SSB index of another SSB through a PBCH-DMRSincluded in another SSB. The UE acquires an SSB index of the neighborcell by commonly applying the 3 MSBs of the SSB index obtained from thePBCH content of the SSB transmitted by the serving cell.

12. Evaluation of Measurement Result

Now, a performance measurement result according to a payload size, atransmission scheme, and a DMRS will be described. It is assumed that 2OFDM symbols having 24 RBs are used to transmit an NR-PBCH. It is alsoassumed that an SS burst set (i.e., 10, 20, 40, or 80 ms) may have aplurality of periodicities and an encoded bit is transmitted within 80ms.

(1) Number of Hypotheses for DMRS Sequence

FIG. 19 illustrates a measurement result according to an SSB index.Herein, 144 REs are used for a DMRS and 432 REs are used forinformation, in 24 RBs and 2 OFDM symbols. It is assumed that a longsequence (e.g., a length-31 Gold sequence) is used as a DMRS sequenceand QPSK is used.

Referring to FIG. 19, when detection performance of 3 to 5 bits isaccumulatively measured, an error rate of 1% is shown in −6 dB.Accordingly, in terms of detection performance, information of 3 to 5bits may be used as the number of hypotheses for the DMRS sequence.

(2) Modulation Type

FIGS. 20 and 21 shows performance measurement results comparing BPSK andQPSK. In this experiment, the number of hypotheses for a DMRS sequenceis 3 bits, the DMRS sequence is based on a long sequence, and a powerlevel of an interference TRP is equal to a power level of a serving TRP.

Referring to FIGS. 20 and 21, it can be appreciated that BPSK is similarin performance to QPSK. Accordingly, even when any modulation type isused for the DMRS sequence, there is little difference in terms ofperformance measurement. However, referring to FIGS. 22 and 23, it canbe appreciated that correlation characteristics differ in BPSK and QPSK.

Referring to FIGS. 22 and 23, more sequences using BPSK are distributedthan those using QPSK in a region in which a correlation amplitude is0.1 or more. Therefore, when a multi-cell environment is considered, itis desirable to use QPSK as a modulation type of the DMRS. That is, interms of a correlation characteristic, QPSK is a more suitablemodulation type for a DMRS sequence.

(3) Sequence Generation of PBCH DMRS

FIGS. 24 and 25 illustrate measurement results according to DMRSsequence generation. A DMRS sequence may be generated based on a longsequence having a polynomial degree of 30 or more and a short sequencehaving a polynomial degree of 8 or less. The number of hypotheses forthe DMRS sequence is 3 bits and a power level of an interference TRP isthe same as that of a serving TRP.

Referring to FIGS. 24 and 25, it can be appreciated that short-sequencebased detection performance is similar to long-sequence based detectionperformance.

Specifically, although it is desired to raise correlation performance ofa sequence by introducing a length-7 polynomial to a first m-sequence,this scheme has little difference with a scheme using a length-31polynomial which is a legacy first m-sequence. In addition, although asequence has been generated using SSBID as an initial value of the firstm-sequence, this scheme has little difference with a scheme of fixing aninitial value of the legacy first m-sequence and using SSBID-CellID fora second m-sequence.

Therefore, a length-31 Gold sequence is used as in LTE, an initial valueof the first m-sequence is fixed for initialization as in a legacyscheme, and SSBID-CellID is applied to the second m-sequence.

(4) DMRS RE Mapping

FIG. 26 illustrates a performance measurement result according to anequal interval RE mapping method and an unequal interval RE mappingmethod. It is assumed that the number of hypotheses for a DMRS sequenceis 3 bits, the DMRS sequence is based on a long sequence, a power levelof an interference TRP is identical to that of a serving TRP, and onlyone interference source is present.

As can be seen from FIG. 26, use of variable RE mapping may cause aneffect of randomly distributing interference. Therefore, detectionperformance of variable RE mapping is better than detection performanceof fixed RE mapping.

FIG. 27 illustrates a measurement result when RS power boosting is used.Herein, it is assumed that RE transmission power for a DMRS is higherthan RE transmission power for PBCH data by about 1.76 dB (=10*log(1.334/0.889)). If both variable RE mapping and DMRS power boosting areused, interference of other cells is reduced. As can be appreciated fromFIG. 27, performance when RS power boosting is applied has gain of 2 or3 dB as compared with the case in which RS power boosting is notpresent.

On the other hand, RS power boosting reduces RE transmission power forthe PBCH data. Therefore, RS power boosting may affect PBCH performance.FIGS. 28 and 29 illustrate results of measuring PBCH performance when RSpower boosting is present and when RS power boosting is not present. Itis assumed that a periodicity of an SS burst set is 40 ms and an encodedbit is transmitted within 80 ms.

If RE transmission power for the PBCH data is reduced, performance lossmay occur. However, since channel estimation performance is improved dueto increase in RS power, demodulation performance can be improved.Accordingly, as can be shown in FIGS. 28 and 29, the two cases exhibitnearly equal performance. Therefore, an effect of transmission powerloss of REs for the PBCH data may be complemented by gain of channelestimation performance.

An experimental observation result of applying Vshift to RS powerboosting will now be described with reference to FIGS. 30 and 31. WhenVshift of changing the position of a DMRS RE on the frequency axisaccording to a cell ID is introduced, if a PBCH DMRS transmitted in amulti-cell environment is received during two periodicities and twoPBCHs are combined, detection performance is improved due to ICIrandomization and, if Vshift is applied, detection performance isremarkably improved.

[Table 3] below shows assumption values of parameters used for theabove-described performance measurement.

TABLE 3 Parameter Value Carrier Frequency 4 GHz Channel Model CDL_C(delay scaling values: 100 ns) Subcarrier Spacing 15 kHz AntennaConfiguration TRP: (1, 1, 2) with Omni-directional antenna element UE:(1, 1, 2) with Omni-directional antenna element Frequency Offset 0% and10% of subcarrier spacing Default period 20 ms Subframe duration 1 msOFDM symbols in SF 14 Number of interfering TRPs 1 Operating SNR −6 dB

13. Half-Frame Index Indication and Signal Design

In addition to the above-described time index indication methods, othertime index indication methods may be considered. Particularly, variousembodiments for effectively indicating a half-frame index will now bedescribed.

SSBs included in a duration of 5 ms may be transmitted at a periodicityof 5 ms, 10 ms, 20 ms, 40 ms, 80 ms, or 160 ms. The UE performs signaldetection in an initial access procedure under the assumption that theSSBs are transmitted at a longer periodicity (e.g., 10 ms or 20 ms) than5 ms. Particularly, in an NR system, the UE of the initial accessprocedure performs signal detection under the assumption that SSBs aretransmitted at a periodicity of 20 ms.

However, if the gNB transmits an SSB at a periodicity of 5 ms and the UEdetects the SSB at a periodicity of 20 ms, the UE should consider thatthe SSB is transmitted in a first radio half-frame and that the SSB istransmitted in a second radio half-frame. That is, the UE cannotaccurately assume that the SSB is received in the first half frame or inthe second half frame. Accordingly, the gNB may consider methods ofaccurately indicating whether the SSB is transmitted in the first halfframe or the second half frame to the UE as follows.

(1) Explicit Indication:

PBCH content is changed at a periodicity of 5 ms. In this case, the UEmay acquire half-frame time information by decoding a received SSB.

(2) Implicit Indication:

A sequence of a PBCH DMRS is changed at a periodicity of 5 ms.

A sequence mapping method of the PBCH DMRS is changed at a periodicityof 5 ms.

Phases of OFDM symbols in which a PBCH is transmitted are shifted at aperiodicity of 5 ms.

Different scrambling sequences are applied to encoded bits of PBCHcontent at a periodicity of 5 ms.

The above methods may be used by a combination thereof and various othermodifications may be made in addition to the above-described methods.Various methods for transmitting half-frame time information may beconsidered according to a situation in which the UE should currentlyreceive time information including a UE state in which the UE is in aninitial access state or an idle mode and a UE situation in which the UEshould perform handover to a neighbor cell (inter-cell)/another RAT(inter-RAT).

Methods of reducing complexity during acquisition of the half-frame timeinformation will now be described.

Embodiment 8-1

The UE of an initial access procedure attempts to detect a signal of anSSB under the assumption that the SSB is transmitted at one fixedposition of either a first half-frame and a second half-frame in a timerange of 10 ms. That is, the UE acquires time information such as an SFNor an SSB index by detecting a sequence included in a signal or achannel included in the SSB or by performing data decoding and acquireshalf-frame information through a slot defined to transmit the SSB in aradio frame or a position of an OFDM symbol.

As a detailed example of the above-described method of acquiring thetime information, a method of allowing the UE performing initial accessto detect only an SSB transmitted in a specific half-frame and notdetect an SSB transmitted in the other half-frame, when SSBs aretransmitted at a periodicity of 5 ms, and an operation of the UE will bedescribed.

For this purpose, two types of SSBs are configured. In the presentdisclosure, for convenience of description, the two types of SSBs arereferred to as a first type of SSB and a second type of SSB. A networkconfigures the first type of SSB and configures the second type of SSBwhich is obtained by shifting a phase of a PSS/SSS/PBCH constituting thefirst type of SSB, a symbol position, a sequence type, a symbol mappingrule, or transmission power.

Next, the gNB transmits the first type of SSB in the first half-frameand transmits the second type of SSB in the second half-frame.

The UE performing initial access attempts to perform SS detection andPBCH decoding under the assumption that the first type of SSB has beentransmitted from the gNB. Upon succeeding in SS detection and PBCHdecoding, the UE assumes that a corresponding point is a slot and OFDMsymbol belonging to the first half-frame.

Embodiment 8-2

As a detailed method of Embodiment 8-1, a method of acquiring half-frameboundary information by shifting phases of some of symbols to whichPSS/SSS/PBCH constituting an SSB are mapped will now be described.

That is, the UE may transmit time information such as an SFN, ahalf-frame, and an SSB index by shifting phases of the PSS/SSS/PBCHconstituting the SSB and particularly transmit the time information ofthe half-frame.

It is assumed that the PSS/SSS/PBCH included in the SSB use the sameantenna port.

Specifically, phases of OFDM symbols including the PSS/SSS and phases ofOFDM symbols including the PBCH may be shifted according to transmissionperiodicity. In this case, the transmission periodicity at which thephases are shifted may be 5 ms.

Referring to FIG. 32, phases of (+1, +1, +1, +1) or (+1, −1, +1, −1) maybe respectively applied to OFDM symbols including PSS-PBCH-SSS-PBCH at aperiodicity of 5 ms. As another method, polarities of the OFDM symbolsincluding the PSS/SSS are inverted. That is, if the polarities of theOFDM symbols including PSS-PBCH-SSS-PBCH are (a, b, c, d), thepolarities of the PBCHs may be inverted to (+1, +1, +1, +1) and (−1, +1,−1, +1). In addition, polarities of some OFDM symbols among the OFDMsymbols including the PSS and the SSS may be inverted to (+1, +1, +1,+1) and (+1, +1, −1, +1) or to (+1, +1, +1, +1) and (−1, +1, +1, +1).

As a specific example of the above method, a method of shifting a phaseat a periodicity of a 20-ms interval may be considered. That is,referring to FIG. 32, phases of a first 5-ms periodicity may betransmitted as (+1, +1, +1, +1), phases of a second 5-ms periodicity maybe transmitted as (+1, −1, +1, −1), phases of a third 5-ms periodicitymay be transmitted as (+1, −1, −1, −1), and phases of a fourth 5-msperiodicity may be transmitted as (−1, −1, −1, −1). Using theabove-described method, boundary information of a 5-ms periodicity,i.e., boundary information of a half-frame, may be acquired. Sincephases are shifted at a periodicity of a 20-ms interval, SFN informationmay also be acquired. However, in order to acquire the SFN information,phases of (+1, +1, +1, +1) may be transmitted in a first 10-ms durationand phases of (+1, −1, +1, −1) may be transmitted in a second 10-msduration, at a periodicity of a 20-ms interval.

Meanwhile, in order to distinguish between periodicities of a 20-msinterval, only phases of the PSS and the SSS included in the SSB may beshifted. For example, phases of the first 5-ms periodicity may betransmitted as (+1, +1, +1, +1) and phases of the second 5-msperiodicity to the fourth 5-ms periodicity may be transmitted as (−1,+1, −1, +1). That is, periodicities of a 20-ms interval may bedistinguished by changing phases of the PSS/SSS of the first 5-msperiodicity and phases of the PSS/SSS of the other 5-ms periodicity.

In this case, SSBs transmitted from the second 5-ms periodicity to thefourth 5-ms periodicity may not be detected by the UE because phases ofthe PSS/SSS are shifted.

Meanwhile, phase change may also be considered together with polarityinversion of a transmitted phase. For example, phases and polarities maybe divided into (+1, +1, +1, +1) and (+1, +j, +1, +j) to transmit theSSB at a periodicity of 5 ms and divided into (+1, +1, +1, +1) and (+1,−j, +1, −j) to transmit the SSB at a periodicity of 5 ms.

The time information of the half-frame may be acquired by shifting aphase of a PBCH symbol and may be used to determine a PBCH scramblingsequence. That is, the gNB configures and transmits the SSB by shiftingphases of an SSS symbol and a PBCH symbol at a periodicity of 5 ms. Inother words, the gNB may shift phases of symbols in which the PBCH andthe SSS of the SSB are transmitted according to a position at which theSSB is transmitted within a specific periodicity. In this case, phasesof symbols of SSSs and PBCHs corresponding to SSBs which are actuallytransmitted by the gNB, rather than phases of symbols of SSSs and PBCHscorresponding to all candidate SSBs in which SSBs can be transmitted,may be shifted.

In other words, phases of symbols corresponding to an SSS and a PBCH ofa candidate SSB which is not actually transmitted may not be shiftedalthough the symbols corresponds to a candidate SSB included in a 5-mshalf-frame.

Detailed methods for the above cases will now be described.

(Method 1) One bit in a PBCH DMRS may be used as an indication forindicating the half-frame. A PBCH scrambling sequence may be initializedby the indication for the half-frame timing. 7 to 10 MSBs of an SFN maybe explicitly indicated through PBCH content and 3 LSBs of the SFN maybe used for the PBCH scrambling sequence.

(Method 2) One bit for the half-frame timing may be indicated by thePBCH. The PBCH scrambling sequence may be initialized by the indicationfor the half-frame timing. In this case, a difference in phase between aPBCH symbol and an SSS symbol may occur. 7 to 10 MSBs of the SFN may beexplicitly indicated through the PBCH content and 3 LSBs of the SFN maybe used for the PBCH scrambling sequence.

(Method 3) One bit for the half-frame timing may be indicated by thePBCH. In this case, a difference in phase between the PBCH symbol andthe SSS symbol may occur. 7 to 10 MSBs of the SFN may be explicitlyindicated through the PBCH content and 3 LSBs of the SFN may be used forthe PBCH scrambling sequence.

Embodiment 8-3

The gNB indicates a transmission periodicity of an actually transmittedSSB to the UE performing measurement and handover. The transmissionperiodicity may be additionally transmitted together with measurementperiodicity information included in measurement related timeinformation. The UE may regard the measurement periodicity informationas transmission periodicity information of the SSB and performmeasurement and handover based on the transmission periodicityinformation. A handover command may include system information relatedto a target cell, such as cell information, SIBs 0, 1, and 2, etc.Meanwhile, for convenience of discussion during design in an NR system,new system information including information of SIBs 0, 1, and 2 definedin LTE is referred to as remaining minimum system information (RMSI).

The above-described RMSI may include information about the position andtransmission periodicity of an actually transmitted SSB in the targetcell. Further, it may be necessary to additionally transmit informationabout SSB transmission periodicities of handover candidate cells as wellas information about an SSB transmission periodicity of the target cell,for the purpose of handover. Therefore, information about SSBtransmission periodicities of candidate cells may be defined as systeminformation different from the handover command and may be transmittedto the UE.

In this case, the operation of the UE will now be described. If an SSBtransmission periodicity longer than 5 ms is indicated, the UE detectsSSs of neighbor cells and acquires time information, i.e., an SSB index,using a first type of SSB. If an SSB transmission periodicity of 5 ms isindicated, the UE detects SSs of neighbor cells and acquires timeinformation, using a first type of SSB and a second type of SSB.

Meanwhile, as a method of reducing reception complexity of the UE, theUE may detect an SSB of a periodicity of 10 ms using the first type ofSSB and attempt to detect an SS and acquire time information usingsecond type of SSB at a time position having an offset of about 5 msbased on the first type of SSB detected in the range of 10 ms afterdetecting the first type of SSB. The UE performing handover using theabove-described method may acquire time information used in a targetcell/candidate cells/target RAT.

Embodiment 8-2 is summarized as follows. If a periodicity for performingmeasurement is transmitted to the UE, a periodicity of an actuallytransmitted SSB is also indicated to the UE. In this case, aconfiguration for measurement may be a periodicity given to performmeasurement in terms of the UE and this periodicity may be configured tobe longer than a transmission periodicity of an SSB actually transmittedby the gNB. This may cause the UE to perform decoding at a periodicityof an actually transmitted SSB upon decoding a PBCH of neighbor cellsbefore handover and reduce UE battery consumption by reducing the numberof times of decoding.

Embodiment 8-4

A channel/signal configuration, a resource configuration scheme, and asequence mapping scheme may be changed according to time informationassumed by the gNB or the state of the UE.

The time information includes an SFN, a slot, an OFDM symbol number, andthe like. A subframe number, a slot number, etc. may be indexed in atime range of M and the subframe number, the slot number, etc. may beindexed in a time range of N less than M. Herein, M=10 ms and N=5 ms.Time indexes defined in different time ranges may be applied accordingto conditions such as time information assumed by the gNB and an accessstate of the UE.

A detailed embodiment of the above example will now be described.

(Method 1) The time information, the channel/signal configuration, orthe resource configuration scheme may be changed according to asynchronization indication indicating a synchronous network or anasynchronous network or an access state of the UE indicating whether thestate of the UE is initial access, handover, or idle/connected mode. Inthis case, the synchronization indication may be transmitted to the UEfrom the gNB.

(Method 2) A sequence mapped to an RS such as a DMRS, a CSI-RS, or anSRS or a scrambling sequence of a data bit such as a PDSCH/PUSCH may bechanged according to the time information such as a slot number or anOFDM symbol number in the range of 10 ms or may be changed at aperiodicity of 5 ms. That is, a CSI-RS resource and a PRACH resource maybe configured based on a radio frame range, a first half-frame range, ora second half-frame range in a range of 10 ms and may be configuredbased on a half-frame at a periodicity of 5 ms.

(Method 3) The channel/signal configuration, the resource configurationscheme, and a sequence mapping scheme may be changed according to abandwidth part. Within a bandwidth part used for initial access, a datachannel such as a PDSCH/PUSCH for carrying broadcasting systeminformation (SI), RACH Msg 2/3/4, and paging, a control channel such asa PDCCH/PUSCH, and an RS such as a DMRS/CRS-RS/SRS/PTRS may beconfigured within an N-time range and may be repeatedly transmitted inan N-time unit. On the other hand, within a bandwidth part configured inan RRC connected state, the data channel, the control channel, and theRS are configured within an M-time range and may be repeatedlytransmitted in an M-time unit.

(Method 4) A PRACH preamble and Msg 2, which are resources used forhandover, may be configured in an M-time range and an N-time range. Forconvenience of description, it is assumed that M=10 ms and N=5 ms.

If the indication indicating the synchronous network is indicated to theUE, the UE assumes that signals transmitted by cells in the samefrequency band have been received within a preset range (e.g., 1 ms) andassumes that 5-ms time information obtained from a serving cell can beequally applied to a neighbor cell as well as the serving cell.

Under this assumption, the UE may use resources configured in the M-timerange. That is, even though there is no transmission of a specificindication by the gNB, the UE may use resources configured in the M-timerange in a circumstance assumed to be the synchronous network.Meanwhile, if the indication indicating the asynchronous network isindicated to the UE or in a circumstance assumed to be the asynchronousnetwork, the UE may use resources configured in the N-time range.

(Method 5) If the indication indicating the synchronous network isindicated to the UE, the UE assumes that signals transmitted by cells inthe same frequency band have been received within a preset range (e.g.,1 ms) and assumes that 5-ms time information obtained from the servingcell can be equally applied to the neighbor cell as well as the servingcell.

14. Bandwidth Part (BWP) for DL Common Channel Transmission

An initial access procedure of LTE is performed within a systembandwidth configured by a master information block (MIB). A PSS/SSS/PBCHis arranged based on the center of the system bandwidth. A common searchspace is defined within the system bandwidth and system information istransmitted by a PDSCH of the common search space allocated within thesystem bandwidth and an RACH procedure for Msg 1/2/3/4 is performed.

An NR system supports an operation within a broadband component carrier(CC), whereas it is very difficult for the UE to be implemented to havecapabilities of performing a necessary operation within all broadbandCCs in terms of cost. Therefore, it may be difficult to smoothlyimplement an initial access procedure within the system bandwidth.

To solve this problem, NR may define a BWP for the initial accessprocedure as illustrated in FIG. 33. In the NR system, the UE mayperform the initial access procedure for SSB transmission, systeminformation transmission, and an RACH procedure within the BWPcorresponding to each UE. At least one DL BWP may include one CORESEThaving the common search space in at least one primary CC.

Accordingly, at least RMSI, OSI, paging, and RACH message 2/4 related DLcontrol information may be transmitted in a CORESET having the commonsearch space and a DL data channel associated with the DL controlinformation may be allocated within a DL BWP. The UE may expect that anSSB will be transmitted within a BWP corresponding thereto.

That is, in NR, at least one DL BWP may be used for DL common channeltransmission. Herein, signals which can be included in the DL commonchannel may include an SSB, a CORSET and RMSI having the common searchspace, OSI, paging, and a PDSCH for RACH messages 2/4. The RMSI may beinterpreted as system information block 1 (SIB1) and is systeminformation that the UE should acquire after receiving an MIB through aPBCH.

(1) Numerology

In NR, subcarrier spacings of 15, 30, 60, and 120 kHz are used for datatransmission. Therefore, numerologies for a PDCCH and a PDSCH within aBWP for the DL common channel may be selected from among numerologiesdefined for data transmission. For example, for the frequency rangebelow 6 GHz, one or more of subcarrier spacings of 15 kHz, 30 kHz, and60 kHz may be selected and, for the frequency range of 6 GHz to 52.6GHz, one or more of subcarrier spacings of 60 kHz and 120 kHz may beselected.

However, since a subcarrier spacing of 60 kHz has already been definedfor a URLLC service in the frequency range below 6 GHz, the subcarrierspacing of 60 kHz is not suitable for PBCH transmission in the frequencyrange below 6 GHz. Accordingly, subcarrier spacings of 15 kHz and 30 kHzmay be used to transmit the DL common channel in the frequency rangebelow 6 GHz, and subcarrier spacings of 60 kHz and 120 kHz may be usedin the frequency range above 6 GHz.

Meanwhile, in NR, subcarrier spacings of 15, 30, 120, and 240 kHz aresupported for SSB transmission. It may be assumed that the samesubcarrier spacing is applied to the CORESET and RMSI having the SSB andthe common search space, paging, and a DL channel such as a PDSCH for anRAR. Hence, when such an assumption is applied, it is not necessary todefine numerology information for PBCH content.

Conversely, the case in which a subcarrier spacing for a DL controlchannel needs to be changed may occur. For example, if a subcarrierspacing of 240 kHz is applied for SSB transmission in the frequency bandabove 6 GHz, since the subcarrier spacing of 240 kHz is not used fordata transmission including DL control channel transmission, it isnecessary to change the subcarrier spacing for data transmissionincluding DL control channel transmission. Therefore, when thesubcarrier spacing can be changed for data transmission including DLdata channel transmission, this may be indicated through a 1-bitindication included in PBCH content. For example, according to a carrierfrequency range, the 1-bit indication may be interpreted as {15 kHz, 30kHz} or {60 kHz, 120 kHz}. The indicated subcarrier spacing may beregarded as a reference numerology of an RB grid. Herein, the PBCHcontent may imply an MIB transmitted in a PBCH.

That is, in the frequency range below 6 GHz, the 1-bit indication mayindicate that a subcarrier spacing for RMSI for initial access, OSI,paging, or Msg 2/4 is 15 kHz or 30 kHz. In the frequency range above 6GHz, the 1-bit indication may indicate that a subcarrier spacing forRMSI for initial access, OSI, paging, or Msg 2/4 is 60 kHz or 120 kHz.

(2) Bandwidth of BWP for DL Common Channel Transmission

In the NR system, a bandwidth of a BWP for a DL common channel need notto be equal to a system bandwidth in which the network operates. Thatis, the bandwidth of the BWP may be narrower than the system bandwidth.That is, the bandwidth should be wider than a minimum carrier bandwidthbut should not be wider than a minimum bandwidth of the UE.

Accordingly, the BWP for DL common channel transmission may be definedsuch that the bandwidth of the BWP is wider than the bandwidth of theSSB and equal to or narrower than a specific DL bandwidth of all UEscapable of operating in each frequency range. For example, in thefrequency range below 6 GHz, the minimum carrier bandwidth may bedefined as 5 MHz and the UE minimum bandwidth may be assumed to be 20MHz. In this case, the bandwidth of a DL common channel may be definedin the range of 5 MHz to 20 MHz. That is, the SSB may be positioned at apart of the DL common channel bandwidth.

(3) Bandwidth Configuration

FIG. 34 illustrates exemplary bandwidth configuration.

The UE attempts to detect a signal within a bandwidth of an SSB duringan initial synchronization procedure including cell ID detection andPBCH decoding. Next, the UE may continue to perform the next initialaccess procedure within a bandwidth for a DL common channel indicated bythe network through PBCH content. That is, the UE may acquire systeminformation within a bandwidth of the DL common channel and perform anRACH procedure.

Meanwhile, an indication for a relative frequency position betweenbandwidth of the SSB and bandwidth of the DL common channel may bedefined in the PBCH content. Meanwhile, as described above, the PBCHcontent may indicate an MIB transmitted in a PBCH.

For example, as illustrated in FIG. 34, a relative frequency positionbetween bandwidth of an SSB and bandwidth of a DL common channel may bedefined as offset information about an interval between bandwidth of theSSB and bandwidth of the DL common channel.

Particularly, referring to FIG. 34, the offset value may be indicated inunits of RBs and the UE may determine that a bandwidth of the DL commonchannel is positioned at an offset position corresponding to the numberof indicated RBs. Meanwhile, in the NR system, numerologies for thebandwidth for the SSB and the bandwidth for the DL common channel, i.e.,subcarrier spacings, may be differently configured. In this case, anabsolute frequency interval of an offset indicated in units of RBs maybe calculated based on any one of a subcarrier spacing of the bandwidthfor the SSB and a subcarrier spacing of the bandwidth for the DL commonchannel.

To simplify an indication of the relative frequency position, abandwidth for a plurality of SSBs may be any one of candidate positionsat which the SSBs are positioned within the bandwidth for the DL commonchannel.

In the NR system, the bandwidth of the DL common channel need not to beequal to a system bandwidth in which the network operates. The bandwidthmay be narrower than the system bandwidth. That is, the bandwidth of theDL common channel should be wider than the minimum carrier bandwidth butshould not be wider than the minimum bandwidth of the UE. For example,the minimum carrier bandwidth in the frequency range below 6 GHz isdefined as 5 MHz. If the minimum bandwidth of the UE is assumed to be 20MHz, the bandwidth of the DL common channel may be defined in the rangeof 5 MHz to 20 MHz.

For example, if the bandwidth of the SSB is 5 MHz and the bandwidth ofthe DL common channel is 20 MHz, 4 candidate positions for detecting theSSBs within the bandwidth for the DL common channel may be defined.

15. CORESET Configuration

(1) CORESET Information and RMSI Scheduling Information

It may be more efficient for a network to transmit CORESET informationincluding RMSI scheduling information to the UE than to directlyindicate the RMSI scheduling information. That is, frequency resourcerelated information, such as CORESET and bandwidth of a frequencyposition, may be indicated through PBCH content. In addition, timeresource related information, such as a start OFDM symbol, a durationtime, and the number of OFDM symbols, may be additionally configured toflexibly use a network resource.

Additionally, the network may also transmit information about a commonsearch space monitoring periodicity, a duration time, and an offset tothe UE in order to reduce detection complexity.

Meanwhile, a transmission type and an REG bundling size may be fixedaccording to CORESET of a common search space. Herein, transmissiontypes may be distinguished according to whether a signal is interleaved.

(2) Number of OFDM Symbols Included in Slot

In association with the number of OFDM symbols in a slot or a carrierfrequency range below 6 GHz, two candidates such as a 7-OFDM symbol slotand a 14-OFDM symbol slot are considered. If the NR system determines tosupport two types of slots for the carrier frequency range below 6 GHz,an indication method for a slot types should be defined to indicate atime resource of the CORESET having the common search space.

(3) Bit Size of PBCH Content

To indicate numerology, bandwidth, and CORESET information in PBCHcontent, about 14 bits may be designated as shown in [Table 4].

TABLE 4 Bit size Details 6 GHz For a6 GHz Reference numerology [1] [1]Bandwidth for DL common channel, [3] [2] and SS block position # of OFDMsymbols in a Slot [1] 0 CORESET About [10] About [10] (Frequencyresource-bandwidth, location) (Time resource-starting OFDM symbol,Duration) (UE Monitoring Periodicity, offset, duration) Total About [14]

FIG. 35 is a block diagram illustrating components of a transmittingdevice 10 and a receiving device 20 which implement the presentdisclosure.

The transmitting device 10 and the receiving device 20, respectivelyinclude radio frequency (RF) units 13 and 23 which transmit or receiveradio signals carrying information/and or data, signals, and messages,memories 12 and 22 which store various types of information related tocommunication in a wireless communication system, and processors 11 and21 which are operatively coupled with components such as the RF units 13and 23 and the memories 12 and 22, and control the memories 12 and 22and/or the RF units 13 and 23 to perform at least one of the foregoingembodiments of the present disclosure.

The memories 12 and 22 may store programs for processing and control ofthe processors 11 and 21, and temporarily store input/outputinformation. The memories 12 and 22 may be used as buffers.

The processors 11 and 21 generally provide overall control to theoperations of various modules in the transmitting device or thereceiving device. Particularly, the processors 11 and 21 may executevarious control functions to implement the present disclosure. Theprocessors 11 and 21 may be called controllers, microcontrollers,microprocessors, microcomputers, and so on. The processors 11 and 21 maybe achieved by various means, for example, hardware, firmware, software,or a combination thereof. In a hardware configuration, the processors 11and 21 may be provided with application specific integrated circuits(ASICs), digital signal processors (DSPs), digital signal processingdevices (DSPDs), programmable logic devices (PLDs), field programmablegate arrays (FPGAs), etc. In a firmware or software configuration,firmware or software may be configured to include a module, a procedure,a function, or the like. The firmware or software configured toimplement the present disclosure may be provided in the processors 11and 21, or may be stored in the memories 12 and 22 and executed by theprocessors 11 and 21.

The processor 11 of the transmitting device 10 performs a predeterminedcoding and modulation on a signal and/or data which is scheduled by theprocessor 11 or a scheduler connected to the processor 11 and will betransmitted to the outside, and then transmits the encoded and modulatedsignal and/or data to the RF unit 13. For example, the processor 11converts a transmission data stream to K layers after demultiplexing,channel encoding, scrambling, modulation, and so on. The encoded datastream is referred to as a codeword, equivalent to a data block providedby the MAC layer, that is, a transport block (TB). One TB is encoded toone codeword, and each codeword is transmitted in the form of one ormore layers to the receiving device. For frequency upconversion, the RFunit 13 may include an oscillator. The RF unit 13 may include Nttransmission antennas (Nt is a positive integer equal to or greater than1).

The signal process of the receiving device 20 is configured to bereverse to the signal process of the transmitting device 10. The RF unit23 of the receiving device 20 receives a radio signal from thetransmitting device 10 under the control of the processor 21. The RFunit 23 may include Nr reception antennas, and recovers a signalreceived through each of the reception antennas to a baseband signal byfrequency downconversion. For the frequency downconversion, the RF unit23 may include an oscillator. The processor 21 may recover the originaldata that the transmitting device 10 intends to transmit by decoding anddemodulating radio signals received through the reception antennas.

Each of the RF units 13 and 23 may include one or more antennas. Theantennas transmit signals processed by the RF units 13 and 23 to theoutside, or receive radio signals from the outside and provide thereceived radio signals to the RF units 13 and 23 under the control ofthe processors 11 and 21 according to an embodiment of the presentdisclosure. An antenna may also be called an antenna port. Each antennamay correspond to one physical antenna or may be configured to be acombination of two or more physical antenna elements. A signaltransmitted from each antenna may not be further decomposed by thereceiving device 20. An RS transmitted in correspondence with acorresponding antenna defines an antenna viewed from the side of thereceiving device 20, and enables the receiving device 20 to performchannel estimation for the antenna, irrespective of whether a channel isa single radio channel from one physical antenna or a composite channelfrom a plurality of physical antenna elements including the antenna.That is, the antenna is defined such that a channel carrying a symbol onthe antenna may be derived from the channel carrying another symbol onthe same antenna. In the case of an RF unit supporting MIMO in whichdata is transmitted and received through a plurality of antennas, the RFunit may be connected to two or more antennas.

In the present disclosure, the RF units 13 and 23 may support receptionBF and transmission BF. For example, the RF units 13 and 23 may beconfigured to perform the exemplary functions described before withreference to FIGS. 5 to 8 in the present disclosure. In addition, the RFunits 13 and 23 may be referred to as transceivers.

In embodiments of the disclosure, a UE operates as the transmittingdevice 10 on UL, and as the receiving device 20 on DL. In theembodiments of the disclosure, the gNB operates as the receiving device20 on UL, and as the transmitting device 10 on DL. Hereinafter, aprocessor, an RF unit, and a memory in a UE are referred to as a UEprocessor, a UE RF unit, and a UE memory, respectively, and a processor,an RF unit, and a memory in a gNB are referred to as a gNB processor, agNB RF unit, and a gNB memory, respectively.

The gNB processor of the present disclosure may perform control to mapan SSB including a PSS/SSS/PBCH to a plurality of symbols and transmitthe SSS to the UE. In this case, depending on whether the SSB istransmitted in a first half-frame or in a second half-frame, a phase ofat least one symbol among the symbols to which the PSS/SSS/PBCH aremapped may be differently mapped. Specifically, the gNB processor maymap and transmit the SSB such that phases of a symbol to which the PBCHis mapped when the SSB is transmitted in a first half-frame and a symbolto which the PBCH is mapped when the SSB is transmitted in a secondhalf-frame may have a difference of 180 degrees, i.e., may be invertedin polarity.

In addition, an indicator for identifying a half-frame in which the SSBis transmitted may be included in the PBCH and a scrambling sequence ofthe PBCH may be generated based on the indicator. A sequence of a PBCHDMRS may be generated based on multiplication of the number of SSBindexes obtainable through the PBCH DMRS and a value (e.g., 0 or 1)indicated by the indicator.

The gNB processor may differently generate the sequence of the PBCH DMRSor may differently map a frequency position to which the PBCH DMRS ismapped, according to a half-frame in which the SSB is transmitted.

Additionally, when the UE performs initial access and when the UE is inan RRC connected state, the gNB processor may transmit the SSB based ona different periodicity, In this case, an SSB transmission periodicitywhen the UE performs initial access may be set to be shorter than an SSBtransmission periodicity when the UE is in the RRC connected state.

The UE processor of the present disclosure may perform control toreceive the SSB including the PSS/SSS/PBCH from the gNB. In this case,the UE processor may identify whether the SSB is received in the firsthalf-frame or in the second half-frame, based on a phase of at least onesymbol among symbols to which the PSS/SSS/PBCH are mapped.

Upon receiving the SSB in the first half-frame, the UE processor mayattempt to detect the SSB transmitted in the second half-frame in aspecific time duration after a predetermined time from a timing at whichthe SSB is received. When synchronization between a serving cell and aneighbor cell is assumed, the UE processor may equally apply timeinformation of the SSB received from the serving cell to the neighborcell.

The gNB processor or the UE processor of the present disclosure may beconfigured to apply the present disclosure in a cell operating in a highfrequency band of 6 GHz or more at which analog or hybrid beamforming isused.

As described before, a detailed description has been given of exemplaryembodiments of the present disclosure so that those skilled in the artmay implement and perform the present disclosure. While reference hasbeen made above to the exemplary embodiments of the present disclosure,those skilled in the art will understand that various modifications andalterations may be made to the present disclosure within the scope ofthe present disclosure. Accordingly, the disclosure should not belimited to the specific examples described herein, but should beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

INDUSTRIAL APPLICABILITY

While the above-described method of transmitting the synchronizationsignal block and the apparatus therefor have been described focusing onan example applied to a 5G new RAT system, the method and apparatus maybe applied to various wireless communication system in addition to the5G new RAT system.

1. A method of receiving a synchronization signal block (SSB) by a userequipment (UE) in a wireless communication system, the methodcomprising: receiving at least one SSB mapped to a plurality of symbolsin a first half-frame or a second half-frame included in a radio frame,wherein the at least one SSB is any one of a first SSB received in thefirst half-frame and a second SSB received in the second half-frame, asignal of the same type is mapped to a first symbol included in aplurality of symbols to which the first SSB is mapped and a secondsymbol included in a plurality of symbols to which the second SSB ismapped, and phases of the first symbol and the second symbol aredifferent.
 2. The method of claim 1, wherein the signal of the same typeis any one of a primary synchronization signal (PSS), a secondarysynchronization signal (SSS), and a physical broadcasting channel(PBCH).
 3. The method of claim 1, wherein the phases of the first symboland the second symbol have a difference of 180 degrees.
 4. The method ofclaim 1, wherein the at least one SSB includes a physical broadcastingchannel (PBCH) including an indicator for distinguishing between thefirst half-frame and the second half-frame, and the indicator is used togenerate a scrambling sequence of the PBCH.
 5. The method of claim 4,wherein a demodulation reference signal (DMRS) is mapped to a symbol towhich the PBCH is mapped, and a sequence of the DMRS is generated basedon the number of SSB indexes obtainable through the DMRS and on theindicator.
 6. The method of claim 5, wherein the sequence of the DMRS isgenerated based on multiplication of the number of the SSB indexesobtainable through the DMRS and a value indicated by the indicator. 7.The method of claim 1, wherein, based on detection of the first SSB, theUE performs detection of the second SSB in a specific time durationafter a predetermined time from a timing at which the first SSB isdetected.
 8. The method of claim 1, wherein a demodulation referencesignal (DMRS) is mapped to a symbol to which a physical broadcastingchannel (PBCH) included in each of the first SSB and the second SSB ismapped, and a sequence of a DMRS related with the first SSB is differentfrom a sequence of a DMRS related with the second SSB.
 9. The method ofclaim 1, wherein a demodulation reference signal (DMRS) is mapped to asymbol to which a physical broadcasting channel (PBCH) included in eachof the first SSB and the second SSB is mapped, and a frequency positionto which a DMRS related with the first SSB is mapped is different from afrequency position to which a DMRS related with the second SSB ismapped.
 10. The method of claim 1, wherein, based on initial accessperformed by the UE, the at least one SSB is repeatedly transmitted at afirst time periodicity, and based on radio resource control (RRC)connection state of the UE, the at least one SSB is repeatedlytransmitted at a second time periodicity longer than the first timeperiodicity.
 11. The method of claim 1, wherein, based on assumptionthat signals transmitted from a serving cell and a neighbor cell of theUE are received within a predetermined error range, time informationobtained through an SSB received from the serving cell is equallyapplied to an SSB received from the neighbor cell.
 12. A user equipment(UE) for receiving a synchronization signal block (SSB) in a wirelesscommunication system, the UE comprising: a transceiver configured totransmit and receive a signal to and from a base station (BS); and aprocessor connected to the transceiver and configured to control thetransceiver to receive at least one SSB mapped to a plurality of symbolsin a first half-frame or a second half-frame included in a radio frame,wherein the at least one SSB is any one of a first SSB received in thefirst half-frame and a second SSB received in the second half-frame, asignal of the same type is mapped to a first symbol included in aplurality of symbols to which the first SSB is mapped and a secondsymbol included in a plurality of symbols to which the second SSB ismapped, and phases of the first symbol and the second symbol aredifferent.
 13. A method of transmitting a synchronization signal block(SSB) by a base station (BS) in a wireless communication system, themethod comprising: mapping at least one SSB to a plurality of symbolsand transmitting the at least one SSB in a first half-frame or a secondhalf-frame included in a radio frame, wherein a first SSB is transmittedin the first half-frame and a second SSB is transmitted in the secondhalf-frame, a signal of the same type is mapped to a first symbolincluded in a plurality of symbols to which the first SSB is mapped anda second symbol included in a plurality of symbols to which the secondSSB is mapped, and phases of the first symbol and the second symbol aredifferently mapped.
 14. A base station (BS) for transmitting asynchronization signal block (SSB) in a wireless communication system,the BS comprising: a transceiver configured to transmit and receive aradio signal to and from a user equipment (UE); and a processorconnected to the transceiver and configured to map at least one SSB to aplurality of symbols and transmit the at least one SSB in a firsthalf-frame or a second half-frame included in a radio frame, wherein afirst SSB is transmitted in the first half-frame and a second SSB istransmitted in the second half-frame, a signal of the same type ismapped to a first symbol included in a plurality of symbols to which thefirst SSB is mapped and a second symbol included in a plurality ofsymbols to which the second SSB is mapped, and phases of the firstsymbol and the second symbol are differently mapped.
 15. The UE of claim12, wherein the UE is capable of communicating with at least one ofanother UE, a UE related to an autonomous driving vehicle, the BS or anetwork.